Of refeeds and diet breaks
Replies
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I’m now only 20lb from goal and set to 1lb per week, but I’ve noticed that I’m occasionally feeling hunger in a way that I wasn’t previously even on fewer calories.
Increased hunger can be a sign of nutrient deprivation. I'd take a look at your diet and try to hit categories you might have been eating less of - fish, eggs, leafy greens, fruits, nuts, etc. A break to fill up on anything that could be lacking may be good, but you could do it without a break too.
I hope this doesn't come off too blunt, but this thread has been a discussion about Lyle McDonald's podcast on refeeds and diet breaks, and supplemented by a few MFP veterans who follow him. I haven't seen you post before, so I'm curious, do you follow Lyle and did you watch the link in the OP?6 -
I have - to my slight embarrassment, now I’ve read this - lost weight continuously for the last year and a half without taking a diet break. There were several occasions that I called ‘diet breaks’, but which were in reality just losing weight more slowly.
I’m now only 20lb from goal and set to 1lb per week, but I’ve noticed that I’m occasionally feeling hunger in a way that I wasn’t previously even on fewer calories.
My question is this: is it worth taking a proper diet break at this point, or have I already screwed up sufficiently that there’s no point and I may as well just keep going until goal?
As most people tend to do. That's completely normal and you're not an outlier. Most people initially permacut and just learn to live with the suck. The larger you are, the longer you can sustain a prolonged deficit. As nihilistic as it sounds, there's going to be an eventual backlash either in the form of increased hunger, reduced activity, lethargy, irritability, etc.
You're just starting to feel that backlash now in the form of ravenous hunger. Again, it's completely normal. You're smaller than you once were and your body wants some of it back. The diet break allows you to eat maintenance calories (calculated at your current bodyweight) for a period of time so that you do get some flexibility by way of increased calories.
You're closer to your goal and while you could white knuckle your way through it, what would you do once you achieve your goal? You'll have to eat at maintenance at some point. Diet breaks serve a dual purpose (I know I've repeated this ad nauseam): 1) you regulate hormonal response and 2) you learn how to eat for the rest of your life to maintain a leaner body fat level.
So do I think a 2+ week diet break is sensible? Yes. You can always go back to a deficit, which is arguably easier than maintenance. Have you screwed up sufficiently? If you're still menstruating and are experiencing amenorrhea, then absolutely take the diet break because that's a sure sign things have gone wrong. If you're still regular, then nothing bad has happened. If you're menopausal and no longer have a menstrual cycle, then hormonal dysregulation can still occur, but that manifests differently which can range anywhere from mild irritation to bouts of deep depression.
A realistic goal to hit for fat loss would be to lose about 0.5-1% per pound of body weight per week. The leaner you are, the lower end of that range will be your target weight loss rate.3 -
Haven't been posting but happily keeping up with everyone's stories!
So my diet break led into the realization that I probably don't need to lose more weight, new goal = recomp. So r-e-a-l-l-y extended diet break
. I read all these posts here about you guys struggling to eat too much and thought, there's NO WAY I would have that problem! And yet here I am often having an extra snack I otherwise wouldn't have even thought about because I need a few more calories.
I guess it makes sense though. I gained weight over the years getting slowly used to a little bit more food and a little bit more food. And so in the process of losing the weight very slowly, I got used to a little bit less food and a little bit less food.
I spent a lot of the last 2 years trying to get in a deficit and not managing to, or hitting the deficit one day and then undoing it the next, so maintaining. But my mindset was always deficit. It's weird not having that in the back of my mind anymore!12 -
Haven't been posting but happily keeping up with everyone's stories!
So my diet break led into the realization that I probably don't need to lose more weight, new goal = recomp. So r-e-a-l-l-y extended diet break . I read all these posts here about you guys struggling to eat too much and thought, there's NO WAY I would have that problem! And yet here I am often having an extra snack I otherwise wouldn't have even thought about because I need a few more calories.
I guess it makes sense though. I gained weight over the years getting slowly used to a little bit more food and a little bit more food. And so in the process of losing the weight very slowly, I got used to a little bit less food and a little bit less food.
I spent a lot of the last 2 years trying to get in a deficit and not managing to, or hitting the deficit one day and then undoing it the next, so maintaining. But my mindset was always deficit. It's weird not having that in the back of my mind anymore!
I've still bumped into the same threads you respond to lol.
And welcome to the recomp club. The painstaking process of feeling like you're spinning your wheels that only becomes apparent that progress is occurring over months, as opposed to weeks.
It's a little bit jarring isn't it? Completely not feeling the need to cut anymore after doing it for so long scares a lot of people.1 -
Haven't been posting but happily keeping up with everyone's stories!
So my diet break led into the realization that I probably don't need to lose more weight, new goal = recomp. So r-e-a-l-l-y extended diet break . I read all these posts here about you guys struggling to eat too much and thought, there's NO WAY I would have that problem! And yet here I am often having an extra snack I otherwise wouldn't have even thought about because I need a few more calories.
I guess it makes sense though. I gained weight over the years getting slowly used to a little bit more food and a little bit more food. And so in the process of losing the weight very slowly, I got used to a little bit less food and a little bit less food.
I spent a lot of the last 2 years trying to get in a deficit and not managing to, or hitting the deficit one day and then undoing it the next, so maintaining. But my mindset was always deficit. It's weird not having that in the back of my mind anymore!
I've still bumped into the same threads you respond to lol.
And welcome to the recomp club. The painstaking process of feeling like you're spinning your wheels that only becomes apparent that progress is occurring over months, as opposed to weeks.
It's a little bit jarring isn't it? Completely not feeling the need to cut anymore after doing it for so long scares a lot of people.
Yeppers, I've seen you wandering around out there in the mfp wild west!
Considering I lost 15 lbs over almost 2 years, and then another 5 lbs over the next year and a half
you'd think spinning my wheels would be old hat by now, but yeah it's weird. I'm unusually patient by nature though, so I'm sure I'll settle into the new mindset soon. It is kind of nice to step on the scale, see I'm still in my range, and know that means job well done. 6 -
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Great job @Hungry_Shopgirl! Feel free to jump in whenever you see fit. It's not going to interrupt the flow. Lol.
In other news, I won the category in the "play stupid games, win stupid prizes" area of training the other night. Long story short, I tried to control drop a clean down to the floor and crashed the barbell square into my quad which resulted in this:
It looked initially worse than it was. My only concern was if I permanently crushed and deformed the muscle, but it was just severe inflammation. Put Lyle's injury book to use again. Quite handy if you haven't looked into it.
Ouch! Hopefully, you’ve fully recovered or are close!
I am 113 posts behind on this thread. Work for the last few weeks has ... sucked. A couple severe mental health issues with students. Trying to support family and friends while I can’t tell them anything by law. Knowing one student isn’t being honest about what’s going on. Finally our threat management consultant was able to tell the family the whole story with legal counsel’s blessing. That’s how bad it was. We technically violated the law but it was the only way we could hope to safety plan. Plus I feel bad for the Student, who is suffering from mental illness.7 -
Some good points. And depletion here being an oversimplification because the body isn't ever going to be truly depleted. In full on ketosis the body still produces enough glycogen for day to day.With refeeds you can completely saturate glycogen in about 2-3 days by eating a buttload of easily digestible carbs and topping off stores in succeeding days. Glycogen depletion occurs when you perform aerobic and total body anaerobic exercise consistently throughout the week while keeping carb intake minimal.
You can replenish glycogen sufficiently in a single day or if you're like me and an amateur competitive eater in a single meal. My latest personal experiments show elevated glucose levels for four days after a re-feed post glycogen depletion (three days fasting).
Glycogen depletion occurs with prolonged caloric deficit and doesn't require exercise for depletion. It also requires both carbohydrate and protein intake reductions as the body can produce substantial glycogen levels from gluconeogensis. My latest personal experiments also show elevated glycogen levels can be maintained on a protein/fat only re-feed for at least three days post glycogen depletion (five days fasting).
Yes, you can replenish glycogen in one day, but the period of not eating slowly dips into liver glycogen, and that period of not eating is sleep. Therefore, you'd have to top it off in the days succeeding day 1.
Liver glycogen depletion occurs with a prolonged caloric deficit. Muscle glycogen doesn't follow that rule. It exists to live for fueling the muscle groups where they reside. Using extended fasting as an example, if you needed to sprint for your life (for whatever reason you want to use), muscle glycogen (and ATP) is used in that process to run like hell.
Gluconeogenesis can replete muscle glycogen in about 18-24 hours after those stores have been used, so to consistently deplete them in preparation for a refeed, you would have to consistently use them. Gluconeogenesis can use any substrate that can be broken down to create carbon, hydrogen, and oxygen molecules.
As for measuring glycogen levels, unless you're taking muscle biopsies and measuring them in a lab, glucose levels only indicate free-floating glucose in the blood, which is not indicative of storage capacity.
For the purposes of a carb refeed, aside from leptin/hormonal regulation, is if you're following CKD, you want to be glycogen depleted from a total body perspective to prime the muscles for an anabolic response to stimulus and that glucose/insulin spike is what's going to be the catalyst for that.
But I'll bite.. what experiments are you running? What's your hypothesis, method, and data from the results you've seen?
But muscular stores run out a bit quicker than you suggest and they are replenished from the body's stores - as mentioned mainly from the liver. Many other energy substrates can be directly consumed such as with the lactic acid shuffle. Cortisol and lactic acid aren't a useless byproduct...
For the experiments mentioned, I was merely testing the ability of protein/fat meals to replenish glycogen stores. In my prior experiments I had a lot of people say gluconeogenesis can't occur to sufficient quantities to replenish stores.
So I fasted for three days, did a carbohydrate re-feed, measured fasting glucose for 5 fasting days to establish a baseline, did a protein/fat only re-feed, then measured glucose over a 4 day fasting period. Crazy enough fasting glucose levels go up (mine around 105 mg/dL on fasted states). While the body is fasted insulin secretion is suppressed to allow the body to transport glycogen stores. Just didn't think it'd be that high... So when it drops below baseline levels I know I am running out of stores. A week long fast will put me at 50 mg/dL.
I do a lot on personal experimentation on cholesterol, fasting glucose, BMR, ketosis, body composition, etc. But that's another story...
Right. Muscle glycogen never gets completely depleted and some do get used upon moderately intense exertion, and protein and fat are sufficient enough to restore muscle glycogen, you’re completely correct, but for those same reasons that they’re effectively constant as they’re replenished by gng, they exist in the muscle to fuel anaerobic activity. The point of glycogen depleting exercise is to use up as much glycogen as possible, typically more than natural replenishment rates, and super compensate glycogen stores.. which in this case, carbs are more effective since they bypass the rate of gng because pure glucose can readily be converted directly to glycogen in the liver.
In ketosis, insulin is suppressed, as you stated, but that also means glucose is spared for parts of the the brain and cells that cannot use ketones or fatty acids as fuel, so in the case of early stages of starvation ketosis (evidenced by extended fasting), gng ramps up to provide glucose for them. When bhb levels reach a high enough blood level, they actually stimulate insulin to inhibit lipolysis for the body to get rid of excess ketones and prevent metabolic acidosis. That insulin surge will incidentally shuttle glucose where it needs to go, either in muscle as glycogen or into fat cells, resultantly dropping blood glucose readings. But circulating blood glucose is not a direct measurement of stored muscle glycogen. I don’t see how it could be without taking a sample of muscle and measuring it in a lab.
All that said, I’m not sure if you’re part of the ketogains or optimising nutrition groups on fb, but you have a pretty good grasp of it for the most part. If you want more background knowledge on ketosis and general physiological responses to substrates read Cahill and Frayn’s work. It’s pretty fascinating. And if you want to use keto for body composition, read Lyle’s book. As far as cholesterol goes, Dave Feldman is pretty much the current low carb/keto experimenter as of late, though Peter Attia is also a lipidologist who went low carb, but I haven’t heard much from him.
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So do I think a 2+ week diet break is sensible? Yes. You can always go back to a deficit, which is arguably easier than maintenance. Have you screwed up sufficiently? If you're still menstruating and are experiencing amenorrhea, then absolutely take the diet break because that's a sure sign things have gone wrong. If you're still regular, then nothing bad has happened. If you're menopausal and no longer have a menstrual cycle, then hormonal dysregulation can still occur, but that manifests differently which can range anywhere from mild irritation to bouts of deep depression.
A realistic goal to hit for fat loss would be to lose about 0.5-1% per pound of body weight per week. The leaner you are, the lower end of that range will be your target weight loss rate.
No amenorrhea, but my periods have changed (in ways I don’t like
). Thanks. I shall attempt to talk my hindbrain into taking a proper diet break, even though it thinks I’m ‘so close’ 4 -
andreascjonsson wrote: »andreascjonsson wrote: »Hi! I am planning on incorperating refeeds in my diet plan. Firstly i read around and saw that they recommend 1 day refeed, bit here it stood that you should have atleast 2 days of refeeds. I am reasonably lean. Would 2 days every 2 weeks be a good place to start? Putting in my pic for reference of my current fitness level. I have been dieting for about 2 and a half months
I'd put you maybe around 18% bf (give or take a couple points in either direction), mostly in the lower abdomen area, which is the primary problem area for men.
That said, you're perfectly fine to do a 2 week deficit > 2 day refeed which is pretty standard. But if you've been strict dieting for 2.5 months, then take a 2 week diet break at your new lower body weight maintenance first. Then go ahead with your plan. If you're not already strength training, focus on that as your primary activity, unless you're a marathon athlete. But I think adding some size to your frame would help offset some of the bf% estimate from a visual aesthetic perspective. You don’t need to fulk and get powerlifter big, I’m just talking general strength training and it’s fine to train like a bodybuilding bro with a various amount of rep ranges for hypertrophy.
Thanks for the helpfull answer! I have been in a deficit for the entire time but 2 weeks feels super long to me since i want to be done cutting as soon as possible. Becouse, just as you point out, my upper body just feels so small atm and i want to start bulking to fix that. I am currently doing strength training and also some mma mixed with 1h cardio sessions.
The reason for the 2 week diet break is for the hormone regulation and psychological reprieve as I outlined above. I mean, sure, you could grind it out longer if you can stand it, but unless you're planning to walk on stage and get judged for being a human string of beef jerky for a few days, it's not worth the struggle IMO. It also gives you an idea of how to eat normally when you're no longer cutting and just eating like a lean human being. No one wants to cut forever, and to gain some size and strength, you're gonna have to be in a slight surplus for a period of time. But without that 2 week maintenance buffer, jumping straight into a bulk the day right after a deficit will shuttle more nutrients for storage than muscle and fuel.
Think of it this way, dieting is slowly starving yourself by depriving the body of nutrients for X amount of time as a loose metaphor. If it suddenly saw all the food, the first thing it wants to do is make damn sure you don't do that again, and will pack it away for a few days before it realizes "Oh, you're not trying to get fat? Oops, well I stored some energy just in case you think about doing that again." The body is hard wired to survive by doing everything it can to avoid discomfort. If getting fat keeps it from suffering, it's going to.
That said, do you have to consistently be on a diet break for 2 weeks? No. You can have a working week of maintenance calories as a diet break before starting another round of cutting. Whether it's optimal, that's subjective, but I certainly don't feel that it adds positive reinforcement to the long-term game of life. The phrasing of "wanting to be done cutting asap" leads me to believe that patience isn't in the cards for your goals.
If patience isn't your strong suit, and you're hellbent on neglecting sound advice, then at least having knowledge on how to safely cut hard and quick for rapid fat loss would be a better tool to use. RFL (https://store.bodyrecomposition.com/product/rapid-fat-loss-handbook/) and/or UD2 (https://store.bodyrecomposition.com/product/the-ultimate-diet/) would be your best bets. UD2 (my recommendation between the two if I had to choose, but both are good) would be used more likely after you've achieved a level of leanness using RFL, but you can also use UD2 solely to meet your body comp needs, since it carries some nuance for a surplus for hypertrophy.
Neither book is a maintenance strategy guide. They're meant to get you to your goal as efficiently as possible. How you learn to keep your ideal body going is going to be dependent on you.
As for your strength training, just follow the rule of progressive overload: increase weights, reps, and/or sets over time and you'll be stronger by virtue of measurable counting. Example: say you can bench 150lbs now for 3 sets of 5 reps. If you are able to bench 155lbs for 3 sets of 5 reps, congrats you got stronger. If you can bench 150lbs for 4 sets of 5 reps, congrats, you got stronger. If you can bench 150 for 3 sets of 6 reps, congrats you got stronger. The way you apply those changes to your needs is still going to be heading towards progress, as long as intensity is present. Benching 95 lbs for 5 sets of 10 reps doesn't do diq if you aren't going to failure. Even then, it's just painfully tedious.
The way Lyle simplifies this boils down to "Lift the thing. Put down the thing. Repeat 2 - 8 times. Add weight to the thing. Repeat as needed."
Thanks again for the insighful answer! I would not mind doing 2 weeks maintenance and then continue cutting if it was not for the fact that im not going to cut much longer. My goal when starting was to hit about 15% bodyfat. I have also been cutting slowly to not lose lean mass, 6 kg in these 2.5 months to be exakt, so about 0.5kg/week.
Now ofcourse i dont want to put on a ton of fat early on in the bulk if i can help it, so i will follow your advice of having 2 weeks of maintenance after the cut to reset abit before starting bulking. I will probably incorperate a diet brake in my next cut. It sounded like you though being in a deficit for 2.5 months was 2 much. For how long do you think one should be in a deficit before the first diet brake, if im also incorperating 2 days of refeed every 2 weeks?2 -
andreascjonsson wrote: »andreascjonsson wrote: »andreascjonsson wrote: »Hi! I am planning on incorperating refeeds in my diet plan. Firstly i read around and saw that they recommend 1 day refeed, bit here it stood that you should have atleast 2 days of refeeds. I am reasonably lean. Would 2 days every 2 weeks be a good place to start? Putting in my pic for reference of my current fitness level. I have been dieting for about 2 and a half months
I'd put you maybe around 18% bf (give or take a couple points in either direction), mostly in the lower abdomen area, which is the primary problem area for men.
That said, you're perfectly fine to do a 2 week deficit > 2 day refeed which is pretty standard. But if you've been strict dieting for 2.5 months, then take a 2 week diet break at your new lower body weight maintenance first. Then go ahead with your plan. If you're not already strength training, focus on that as your primary activity, unless you're a marathon athlete. But I think adding some size to your frame would help offset some of the bf% estimate from a visual aesthetic perspective. You don’t need to fulk and get powerlifter big, I’m just talking general strength training and it’s fine to train like a bodybuilding bro with a various amount of rep ranges for hypertrophy.
Thanks for the helpfull answer! I have been in a deficit for the entire time but 2 weeks feels super long to me since i want to be done cutting as soon as possible. Becouse, just as you point out, my upper body just feels so small atm and i want to start bulking to fix that. I am currently doing strength training and also some mma mixed with 1h cardio sessions.
The reason for the 2 week diet break is for the hormone regulation and psychological reprieve as I outlined above. I mean, sure, you could grind it out longer if you can stand it, but unless you're planning to walk on stage and get judged for being a human string of beef jerky for a few days, it's not worth the struggle IMO. It also gives you an idea of how to eat normally when you're no longer cutting and just eating like a lean human being. No one wants to cut forever, and to gain some size and strength, you're gonna have to be in a slight surplus for a period of time. But without that 2 week maintenance buffer, jumping straight into a bulk the day right after a deficit will shuttle more nutrients for storage than muscle and fuel.
Think of it this way, dieting is slowly starving yourself by depriving the body of nutrients for X amount of time as a loose metaphor. If it suddenly saw all the food, the first thing it wants to do is make damn sure you don't do that again, and will pack it away for a few days before it realizes "Oh, you're not trying to get fat? Oops, well I stored some energy just in case you think about doing that again." The body is hard wired to survive by doing everything it can to avoid discomfort. If getting fat keeps it from suffering, it's going to.
That said, do you have to consistently be on a diet break for 2 weeks? No. You can have a working week of maintenance calories as a diet break before starting another round of cutting. Whether it's optimal, that's subjective, but I certainly don't feel that it adds positive reinforcement to the long-term game of life. The phrasing of "wanting to be done cutting asap" leads me to believe that patience isn't in the cards for your goals.
If patience isn't your strong suit, and you're hellbent on neglecting sound advice, then at least having knowledge on how to safely cut hard and quick for rapid fat loss would be a better tool to use. RFL (https://store.bodyrecomposition.com/product/rapid-fat-loss-handbook/) and/or UD2 (https://store.bodyrecomposition.com/product/the-ultimate-diet/) would be your best bets. UD2 (my recommendation between the two if I had to choose, but both are good) would be used more likely after you've achieved a level of leanness using RFL, but you can also use UD2 solely to meet your body comp needs, since it carries some nuance for a surplus for hypertrophy.
Neither book is a maintenance strategy guide. They're meant to get you to your goal as efficiently as possible. How you learn to keep your ideal body going is going to be dependent on you.
As for your strength training, just follow the rule of progressive overload: increase weights, reps, and/or sets over time and you'll be stronger by virtue of measurable counting. Example: say you can bench 150lbs now for 3 sets of 5 reps. If you are able to bench 155lbs for 3 sets of 5 reps, congrats you got stronger. If you can bench 150lbs for 4 sets of 5 reps, congrats, you got stronger. If you can bench 150 for 3 sets of 6 reps, congrats you got stronger. The way you apply those changes to your needs is still going to be heading towards progress, as long as intensity is present. Benching 95 lbs for 5 sets of 10 reps doesn't do diq if you aren't going to failure. Even then, it's just painfully tedious.
The way Lyle simplifies this boils down to "Lift the thing. Put down the thing. Repeat 2 - 8 times. Add weight to the thing. Repeat as needed."
Thanks again for the insighful answer! I would not mind doing 2 weeks maintenance and then continue cutting if it was not for the fact that im not going to cut much longer. My goal when starting was to hit about 15% bodyfat. I have also been cutting slowly to not lose lean mass, 6 kg in these 2.5 months to be exakt, so about 0.5kg/week.
Now ofcourse i dont want to put on a ton of fat early on in the bulk if i can help it, so i will follow your advice of having 2 weeks of maintenance after the cut to reset abit before starting bulking. I will probably incorperate a diet brake in my next cut. It sounded like you though being in a deficit for 2.5 months was 2 much. For how long do you think one should be in a deficit before the first diet brake, if im also incorperating 2 days of refeed every 2 weeks?
12-15% is a good level of bf to be when bulking. I mean you could start now, but that results in going back to a deficit later to lose expected fat gain.
As for how long you need to be in a deficit, it’s also subjective but at your current level, probably 4-8 weeks before taking a diet break and assessing whether you need another round of cutting. Just so we’re on the same page, when I say a period of a deficit, your 4-8 week average (including the weekly 2-day refeeds) calorie intake still results in a net deficit.
If you want to properly apply the diet break coming off a deficit (in terms of hormonal regulation), you actually can be in a *slight* surplus (~10% above maintenance) for the first 2-3 days (usually the refeed days), then drop it back to maintenance for the remainder of the diet break period.
To address the rate of weight loss to minimize lean mass loss, that’s ultimately determined by the amount of protein you eat and muscle stimulus to preserve it.
The equation works out to be muscle protein synthesis - muscle protein breakdown = net muscle mass. We aren’t able to determine that rate without biopsies, so the best we can do is measure strength output and size, to a degree. If you’re getting stronger, even in a deficit, you’re likely retaining muscle, and if you’re a novice, increase in muscle size (aka gains) and getting stronger, you’re likely gaining muscle. If you’re getting weaker and/or noticeably losing size in areas of muscle measurement, you would be losing.
So, in a deficit, a focus on strength training retains (or possibly gains) muscle - more protein is needed. In a surplus, focus on strength training to gain muscle - sufficient protein is needed. In maintenance, focus on strength training to maintain and even gain muscle - sufficient protein is needed.
There’s a pattern. I’m not saying to take away from your mma training, just on your lifting days, give it max effort with intensity (exerting enough force to successfully lift a load that elicits a growth response). It doesn’t need to be long and tedious. In fact, you ideally want to do the minimal effective amount of work that provides growth. Push, pull, legs is the standard full body workout and it can be done 3 days a week. To make it short and sweet, you can superset the push and pull, then focus on legs after.2 -
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Muscle biopsy wouldn't be a good measure as glycogen storage is non-uniform distribution. Even if one area was depleted no telling if that means another is...
Some good points. And depletion here being an oversimplification because the body isn't ever going to be truly depleted. In full on ketosis the body still produces enough glycogen for day to day.With refeeds you can completely saturate glycogen in about 2-3 days by eating a buttload of easily digestible carbs and topping off stores in succeeding days. Glycogen depletion occurs when you perform aerobic and total body anaerobic exercise consistently throughout the week while keeping carb intake minimal.
You can replenish glycogen sufficiently in a single day or if you're like me and an amateur competitive eater in a single meal. My latest personal experiments show elevated glucose levels for four days after a re-feed post glycogen depletion (three days fasting).
Glycogen depletion occurs with prolonged caloric deficit and doesn't require exercise for depletion. It also requires both carbohydrate and protein intake reductions as the body can produce substantial glycogen levels from gluconeogensis. My latest personal experiments also show elevated glycogen levels can be maintained on a protein/fat only re-feed for at least three days post glycogen depletion (five days fasting).
Yes, you can replenish glycogen in one day, but the period of not eating slowly dips into liver glycogen, and that period of not eating is sleep. Therefore, you'd have to top it off in the days succeeding day 1.
Liver glycogen depletion occurs with a prolonged caloric deficit. Muscle glycogen doesn't follow that rule. It exists to live for fueling the muscle groups where they reside. Using extended fasting as an example, if you needed to sprint for your life (for whatever reason you want to use), muscle glycogen (and ATP) is used in that process to run like hell.
Gluconeogenesis can replete muscle glycogen in about 18-24 hours after those stores have been used, so to consistently deplete them in preparation for a refeed, you would have to consistently use them. Gluconeogenesis can use any substrate that can be broken down to create carbon, hydrogen, and oxygen molecules.
As for measuring glycogen levels, unless you're taking muscle biopsies and measuring them in a lab, glucose levels only indicate free-floating glucose in the blood, which is not indicative of storage capacity.
For the purposes of a carb refeed, aside from leptin/hormonal regulation, is if you're following CKD, you want to be glycogen depleted from a total body perspective to prime the muscles for an anabolic response to stimulus and that glucose/insulin spike is what's going to be the catalyst for that.
But I'll bite.. what experiments are you running? What's your hypothesis, method, and data from the results you've seen?
But muscular stores run out a bit quicker than you suggest and they are replenished from the body's stores - as mentioned mainly from the liver. Many other energy substrates can be directly consumed such as with the lactic acid shuffle. Cortisol and lactic acid aren't a useless byproduct...
For the experiments mentioned, I was merely testing the ability of protein/fat meals to replenish glycogen stores. In my prior experiments I had a lot of people say gluconeogenesis can't occur to sufficient quantities to replenish stores.
So I fasted for three days, did a carbohydrate re-feed, measured fasting glucose for 5 fasting days to establish a baseline, did a protein/fat only re-feed, then measured glucose over a 4 day fasting period. Crazy enough fasting glucose levels go up (mine around 105 mg/dL on fasted states). While the body is fasted insulin secretion is suppressed to allow the body to transport glycogen stores. Just didn't think it'd be that high... So when it drops below baseline levels I know I am running out of stores. A week long fast will put me at 50 mg/dL.
I do a lot on personal experimentation on cholesterol, fasting glucose, BMR, ketosis, body composition, etc. But that's another story...
Right. Muscle glycogen never gets completely depleted and some do get used upon moderately intense exertion, and protein and fat are sufficient enough to restore muscle glycogen, you’re completely correct, but for those same reasons that they’re effectively constant as they’re replenished by gng, they exist in the muscle to fuel anaerobic activity. The point of glycogen depleting exercise is to use up as much glycogen as possible, typically more than natural replenishment rates, and super compensate glycogen stores.. which in this case, carbs are more effective since they bypass the rate of gng because pure glucose can readily be converted directly to glycogen in the liver.
In ketosis, insulin is suppressed, as you stated, but that also means glucose is spared for parts of the the brain and cells that cannot use ketones or fatty acids as fuel, so in the case of early stages of starvation ketosis (evidenced by extended fasting), gng ramps up to provide glucose for them. When bhb levels reach a high enough blood level, they actually stimulate insulin to inhibit lipolysis for the body to get rid of excess ketones and prevent metabolic acidosis. That insulin surge will incidentally shuttle glucose where it needs to go, either in muscle as glycogen or into fat cells, resultantly dropping blood glucose readings. But circulating blood glucose is not a direct measurement of stored muscle glycogen. I don’t see how it could be without taking a sample of muscle and measuring it in a lab.
All that said, I’m not sure if you’re part of the ketogains or optimising nutrition groups on fb, but you have a pretty good grasp of it for the most part. If you want more background knowledge on ketosis and general physiological responses to substrates read Cahill and Frayn’s work. It’s pretty fascinating. And if you want to use keto for body composition, read Lyle’s book. As far as cholesterol goes, Dave Feldman is pretty much the current low carb/keto experimenter as of late, though Peter Attia is also a lipidologist who went low carb, but I haven’t heard much from him.
Fasting glucose levels during extended fasting periods is a good reflection of when stores run out. Simply put, the body is going to replenish muscle stores from organ stores until it starts running out. If the body stores enough glycogen for three days you'd expect to see elevated levels post refeed then a drop after the three day mark - which is exactly what I observed on 3 of 3 occasions so far.
Unless you want to suggest that after three days of fasting dropping glucose levels aren't a biological indicator of stores running out?
I'm suggesting that circulating blood glucose is a direct measurement of circulating blood glucose. How that translates to stored muscle glycogen depletion is completely separate. Liver glycogen freely releases glycogen for blood glucose, but skeletal muscle glycogen exists only to be used by the muscle for anaerobic activity, not released passively.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3248697/
Just as a visual representation, consider that a freeway represents your blood stream, and the cars on that freeway represent blood glucose molecules. When there is little traffic on that freeway, just because there are very few cars does not mean they somehow just disappeared, rather they are stored elsewhere, and in this example, storage is either muscle glycogen or fat cells.
In terms of ketosis induced fasting metabolism on glucose, the basal insulin response due to insulin sensitivity regulates blood glucose levels so a drop in fasting glucose is merely a physiological response to keep it regulated. Hepatic glycogen freely gets depleted during fasting, and I understand what you're trying to convey, but liver glycogen is not muscle glycogen.
https://sci-hub.tw/https://doi.org/10.1016/S0300-595X(76)80028-X
As for direct measurement of skeletal muscle glycogen, biopsies have been the clinical gold standard of glycogen measurement.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5371784/3 -
I have - to my slight embarrassment, now I’ve read this - lost weight continuously for the last year and a half without taking a diet break. There were several occasions that I called ‘diet breaks’, but which were in reality just losing weight more slowly.
I’m now only 20lb from goal and set to 1lb per week, but I’ve noticed that I’m occasionally feeling hunger in a way that I wasn’t previously even on fewer calories.
My question is this: is it worth taking a proper diet break at this point, or have I already screwed up sufficiently that there’s no point and I may as well just keep going until goal?
*waves* glad you found the thread! 3 -
I have - to my slight embarrassment, now I’ve read this - lost weight continuously for the last year and a half without taking a diet break. There were several occasions that I called ‘diet breaks’, but which were in reality just losing weight more slowly.
I’m now only 20lb from goal and set to 1lb per week, but I’ve noticed that I’m occasionally feeling hunger in a way that I wasn’t previously even on fewer calories.
My question is this: is it worth taking a proper diet break at this point, or have I already screwed up sufficiently that there’s no point and I may as well just keep going until goal?
As most people tend to do. That's completely normal and you're not an outlier. Most people initially permacut and just learn to live with the suck. The larger you are, the longer you can sustain a prolonged deficit. As nihilistic as it sounds, there's going to be an eventual backlash either in the form of increased hunger, reduced activity, lethargy, irritability, etc.
You're just starting to feel that backlash now in the form of ravenous hunger. Again, it's completely normal. You're smaller than you once were and your body wants some of it back. The diet break allows you to eat maintenance calories (calculated at your current bodyweight) for a period of time so that you do get some flexibility by way of increased calories.
You're closer to your goal and while you could white knuckle your way through it, what would you do once you achieve your goal? You'll have to eat at maintenance at some point. Diet breaks serve a dual purpose (I know I've repeated this ad nauseam): 1) you regulate hormonal response and 2) you learn how to eat for the rest of your life to maintain a leaner body fat level.
So do I think a 2+ week diet break is sensible? Yes. You can always go back to a deficit, which is arguably easier than maintenance. Have you screwed up sufficiently? If you're still menstruating and are experiencing amenorrhea, then absolutely take the diet break because that's a sure sign things have gone wrong. If you're still regular, then nothing bad has happened. If you're menopausal and no longer have a menstrual cycle, then hormonal dysregulation can still occur, but that manifests differently which can range anywhere from mild irritation to bouts of deep depression.
A realistic goal to hit for fat loss would be to lose about 0.5-1% per pound of body weight per week. The leaner you are, the lower end of that range will be your target weight loss rate.
That's good to know for me, too. I haven't really taken a true diet break since I started last year, but haven't had any of the really bad signs you mentioned - I was just starting into feeling deprived. Raising my calories this week really did help, though I still lost weight, so I may need to up it again next week until I can find true maintenance level as I really had no idea where maintenance was.
My sister who is also badly obese with a BMI of a little over 50 has just started calorie counting at about a pound and a quarter deficit (she's only 5'2" and I didn't want to really jar her with the deficit since she had been eating for years way over her maintenance levels). For someone who is greatly obese, what again was the recommended intervals for diet breaks? I'd like to start her off right and learn from my mistakes!1 -
Haven't been posting but happily keeping up with everyone's stories!
So my diet break led into the realization that I probably don't need to lose more weight, new goal = recomp. So r-e-a-l-l-y extended diet break . I read all these posts here about you guys struggling to eat too much and thought, there's NO WAY I would have that problem! And yet here I am often having an extra snack I otherwise wouldn't have even thought about because I need a few more calories.
I guess it makes sense though. I gained weight over the years getting slowly used to a little bit more food and a little bit more food. And so in the process of losing the weight very slowly, I got used to a little bit less food and a little bit less food.
I spent a lot of the last 2 years trying to get in a deficit and not managing to, or hitting the deficit one day and then undoing it the next, so maintaining. But my mindset was always deficit. It's weird not having that in the back of my mind anymore!
I've still bumped into the same threads you respond to lol.
And welcome to the recomp club. The painstaking process of feeling like you're spinning your wheels that only becomes apparent that progress is occurring over months, as opposed to weeks.
It's a little bit jarring isn't it? Completely not feeling the need to cut anymore after doing it for so long scares a lot of people.
Yeppers, I've seen you wandering around out there in the mfp wild west!
Considering I lost 15 lbs over almost 2 years, and then another 5 lbs over the next year and a half you'd think spinning my wheels would be old hat by now, but yeah it's weird. I'm unusually patient by nature though, so I'm sure I'll settle into the new mindset soon. It is kind of nice to step on the scale, see I'm still in my range, and know that means job well done.
I think you might have been around MFP long enough to have seen the threads in their infancy when it was a true wild west haha, but seems like nothing has changed much. At least there aren't threads making claims that peeing out white stuff is the body getting rid of fat. That thread is forever burned into memory and I think it's about 6 years old?
At least with recomp, you know that you can measure success by progressively increasing strength, new vascularity, and/or suddenly seeing muscle definition you haven't seen before if remaining around the same weight. These are objective measurements of progress. If nothing changes, well, then .. time to get some new tires (>_<)2 -
Haven't been posting but happily keeping up with everyone's stories!
So my diet break led into the realization that I probably don't need to lose more weight, new goal = recomp. So r-e-a-l-l-y extended diet break . I read all these posts here about you guys struggling to eat too much and thought, there's NO WAY I would have that problem! And yet here I am often having an extra snack I otherwise wouldn't have even thought about because I need a few more calories.
I guess it makes sense though. I gained weight over the years getting slowly used to a little bit more food and a little bit more food. And so in the process of losing the weight very slowly, I got used to a little bit less food and a little bit less food.
I spent a lot of the last 2 years trying to get in a deficit and not managing to, or hitting the deficit one day and then undoing it the next, so maintaining. But my mindset was always deficit. It's weird not having that in the back of my mind anymore!
I've still bumped into the same threads you respond to lol.
And welcome to the recomp club. The painstaking process of feeling like you're spinning your wheels that only becomes apparent that progress is occurring over months, as opposed to weeks.
It's a little bit jarring isn't it? Completely not feeling the need to cut anymore after doing it for so long scares a lot of people.
Yeppers, I've seen you wandering around out there in the mfp wild west!
Considering I lost 15 lbs over almost 2 years, and then another 5 lbs over the next year and a half you'd think spinning my wheels would be old hat by now, but yeah it's weird. I'm unusually patient by nature though, so I'm sure I'll settle into the new mindset soon. It is kind of nice to step on the scale, see I'm still in my range, and know that means job well done.
I think you might have been around MFP long enough to have seen the threads in their infancy when it was a true wild west haha, but seems like nothing has changed much. At least there aren't threads making claims that peeing out white stuff is the body getting rid of fat. That thread is forever burned into memory and I think it's about 6 years old?
At least with recomp, you know that you can measure success by progressively increasing strength, new vascularity, and/or suddenly seeing muscle definition you haven't seen before if remaining around the same weight. These are objective measurements of progress. If nothing changes, well, then .. time to get some new tires (>_<)
My face literally made the "woo" expression reading this.4 -
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bmeadows380 wrote: »I have - to my slight embarrassment, now I’ve read this - lost weight continuously for the last year and a half without taking a diet break. There were several occasions that I called ‘diet breaks’, but which were in reality just losing weight more slowly.
I’m now only 20lb from goal and set to 1lb per week, but I’ve noticed that I’m occasionally feeling hunger in a way that I wasn’t previously even on fewer calories.
My question is this: is it worth taking a proper diet break at this point, or have I already screwed up sufficiently that there’s no point and I may as well just keep going until goal?
As most people tend to do. That's completely normal and you're not an outlier. Most people initially permacut and just learn to live with the suck. The larger you are, the longer you can sustain a prolonged deficit. As nihilistic as it sounds, there's going to be an eventual backlash either in the form of increased hunger, reduced activity, lethargy, irritability, etc.
You're just starting to feel that backlash now in the form of ravenous hunger. Again, it's completely normal. You're smaller than you once were and your body wants some of it back. The diet break allows you to eat maintenance calories (calculated at your current bodyweight) for a period of time so that you do get some flexibility by way of increased calories.
You're closer to your goal and while you could white knuckle your way through it, what would you do once you achieve your goal? You'll have to eat at maintenance at some point. Diet breaks serve a dual purpose (I know I've repeated this ad nauseam): 1) you regulate hormonal response and 2) you learn how to eat for the rest of your life to maintain a leaner body fat level.
So do I think a 2+ week diet break is sensible? Yes. You can always go back to a deficit, which is arguably easier than maintenance. Have you screwed up sufficiently? If you're still menstruating and are experiencing amenorrhea, then absolutely take the diet break because that's a sure sign things have gone wrong. If you're still regular, then nothing bad has happened. If you're menopausal and no longer have a menstrual cycle, then hormonal dysregulation can still occur, but that manifests differently which can range anywhere from mild irritation to bouts of deep depression.
A realistic goal to hit for fat loss would be to lose about 0.5-1% per pound of body weight per week. The leaner you are, the lower end of that range will be your target weight loss rate.
That's good to know for me, too. I haven't really taken a true diet break since I started last year, but haven't had any of the really bad signs you mentioned - I was just starting into feeling deprived. Raising my calories this week really did help, though I still lost weight, so I may need to up it again next week until I can find true maintenance level as I really had no idea where maintenance was.
My sister who is also badly obese with a BMI of a little over 50 has just started calorie counting at about a pound and a quarter deficit (she's only 5'2" and I didn't want to really jar her with the deficit since she had been eating for years way over her maintenance levels). For someone who is greatly obese, what again was the recommended intervals for diet breaks? I'd like to start her off right and learn from my mistakes!
Just as a follow up to the menses dysfunction statement, if as a woman, you've become irregular or completely stopped menstruating, the diet break is going to last as long as it needs to regulate hormones to produce a regular period again. This is hopefully obvious that it's going to be longer than 2 weeks. It may take over a month or longer, but if it happens, by all means do not reverse diet back into maintenance. Remember that reverse dieting is just extending the deficit period until maintenance is achieved. Scale weight and body composition goals take a backseat to immediately shift over to the hugely more important function of your reproductive and overall health.
If you want to get a rough estimate of maintenance, multiply your current body weight x 12-14 as a woman. For men, it's usually 13-15. The more active they are, use the higher end. The more sedentary, use the lower end.
For someone who is greatly obese and just starting, the initial stage of success begins with them being able to be comfortable with being on a diet in the first place. As tough as it is, there's no amount of forcing, arguing, or shaming someone into a diet. It produces the opposite effect most of the time. Use positive reinforcement and encouragement strategies if they're open to the idea. You said she just started counting, so that's already a good start for her.
If you want to start them off right, politely educate them on recognizing what calories are, how to read nutrition labels and note that serving size calories are not the same as calories for the entire package, and help them ease into the diet by finding out their food preference. They don't need to be concerned with macros at the moment, but they'll eventually need to at least get a basic understanding that protein, carbs, fat, and fiber are what make up the source of all food. If they prefer more fatty food over carbs, then a lower carb diet will be effective. If they prefer more carbs than fatty food, then a lower fat diet will be effective. If they have no preference, then an equal split between carbs and fat are fine.
Perhaps the priority macro to get them to understand is protein. It would be difficult to suggest an accurate gram per lbm in the obese, so in this case we will use grams per pound of body weight. Obese dieters can be fine at about 0.5-0.7g/lb of bodyweight. For example, a 250 lb dieter will be perfectly fine on 125-175g of protein. They have more than enough stored energy to spare lean mass from wasting. At the same time, if they focus on natural sources of protein (avoid supplements if possible), it almost always prevents them from overeating if that's the focus of their meals.
As for how long, it will be dependent on their adherence. Understand that the new dieter is going to make mistakes early in their fat loss journey. Encourage them that it's okay and it's just a learning process. They can potentially be at it for months before seeing steady progress. That said, it's not uncommon for morbidly obese dieters to lose a rate up to 1.5% of their body weight per week, especially early on. It becomes a positive feedback loop for them because as they see progress, the more they want to keep at it. This leads to many of us cutting consistently for months or even years in some cases.
Remember that the larger a person starts their diet, the longer they're able to sustain a longer period of dieting, and conversely they're able to sustain a steep deficit for longer as well, and in the case of obese dieters on a psmf, they were able to adhere to it for 17 +/- 12 weeks and a refeed/maintenance period of 9 +/- 12 weeks (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1646394/).
Basically what this means is as long as she can tolerate her deficit, she should be on it as long as she wants. She should be aware that there is inevitably going to be some lingering hunger, some mild mood discomfort, and some craving days. That's inevitable. Now, if she's having a noticeably adverse reaction to the diet by having wild mood swings, binging, depression, etc., then include the diet break to maintenance using her body weight at the time of needing one. After the diet break, resume another round of dieting to tolerance.
TL;DR = Find out the necessary deficit calorie goal > use 0.5-0.7g/lb of protein for the obese dieter to calculate remaining calories for carbs/fat depending on their preference > learn about nutrient density and food quality > diet as long as necessary (12 weeks on average, but can be more or less) before needing a diet break > resume and repeat dieting/break cycles. Once they've achieved an average body fat % (25-31% for women), increase protein to ~0.7-0.8g/lb. As they get leaner, protein needs increase and dieting periods decrease.7 -
Muscle biopsy wouldn't be a good measure as glycogen storage is non-uniform distribution. Even if one area was depleted no telling if that means another is...
Some good points. And depletion here being an oversimplification because the body isn't ever going to be truly depleted. In full on ketosis the body still produces enough glycogen for day to day.With refeeds you can completely saturate glycogen in about 2-3 days by eating a buttload of easily digestible carbs and topping off stores in succeeding days. Glycogen depletion occurs when you perform aerobic and total body anaerobic exercise consistently throughout the week while keeping carb intake minimal.
You can replenish glycogen sufficiently in a single day or if you're like me and an amateur competitive eater in a single meal. My latest personal experiments show elevated glucose levels for four days after a re-feed post glycogen depletion (three days fasting).
Glycogen depletion occurs with prolonged caloric deficit and doesn't require exercise for depletion. It also requires both carbohydrate and protein intake reductions as the body can produce substantial glycogen levels from gluconeogensis. My latest personal experiments also show elevated glycogen levels can be maintained on a protein/fat only re-feed for at least three days post glycogen depletion (five days fasting).
Yes, you can replenish glycogen in one day, but the period of not eating slowly dips into liver glycogen, and that period of not eating is sleep. Therefore, you'd have to top it off in the days succeeding day 1.
Liver glycogen depletion occurs with a prolonged caloric deficit. Muscle glycogen doesn't follow that rule. It exists to live for fueling the muscle groups where they reside. Using extended fasting as an example, if you needed to sprint for your life (for whatever reason you want to use), muscle glycogen (and ATP) is used in that process to run like hell.
Gluconeogenesis can replete muscle glycogen in about 18-24 hours after those stores have been used, so to consistently deplete them in preparation for a refeed, you would have to consistently use them. Gluconeogenesis can use any substrate that can be broken down to create carbon, hydrogen, and oxygen molecules.
As for measuring glycogen levels, unless you're taking muscle biopsies and measuring them in a lab, glucose levels only indicate free-floating glucose in the blood, which is not indicative of storage capacity.
For the purposes of a carb refeed, aside from leptin/hormonal regulation, is if you're following CKD, you want to be glycogen depleted from a total body perspective to prime the muscles for an anabolic response to stimulus and that glucose/insulin spike is what's going to be the catalyst for that.
But I'll bite.. what experiments are you running? What's your hypothesis, method, and data from the results you've seen?
But muscular stores run out a bit quicker than you suggest and they are replenished from the body's stores - as mentioned mainly from the liver. Many other energy substrates can be directly consumed such as with the lactic acid shuffle. Cortisol and lactic acid aren't a useless byproduct...
For the experiments mentioned, I was merely testing the ability of protein/fat meals to replenish glycogen stores. In my prior experiments I had a lot of people say gluconeogenesis can't occur to sufficient quantities to replenish stores.
So I fasted for three days, did a carbohydrate re-feed, measured fasting glucose for 5 fasting days to establish a baseline, did a protein/fat only re-feed, then measured glucose over a 4 day fasting period. Crazy enough fasting glucose levels go up (mine around 105 mg/dL on fasted states). While the body is fasted insulin secretion is suppressed to allow the body to transport glycogen stores. Just didn't think it'd be that high... So when it drops below baseline levels I know I am running out of stores. A week long fast will put me at 50 mg/dL.
I do a lot on personal experimentation on cholesterol, fasting glucose, BMR, ketosis, body composition, etc. But that's another story...
Right. Muscle glycogen never gets completely depleted and some do get used upon moderately intense exertion, and protein and fat are sufficient enough to restore muscle glycogen, you’re completely correct, but for those same reasons that they’re effectively constant as they’re replenished by gng, they exist in the muscle to fuel anaerobic activity. The point of glycogen depleting exercise is to use up as much glycogen as possible, typically more than natural replenishment rates, and super compensate glycogen stores.. which in this case, carbs are more effective since they bypass the rate of gng because pure glucose can readily be converted directly to glycogen in the liver.
In ketosis, insulin is suppressed, as you stated, but that also means glucose is spared for parts of the the brain and cells that cannot use ketones or fatty acids as fuel, so in the case of early stages of starvation ketosis (evidenced by extended fasting), gng ramps up to provide glucose for them. When bhb levels reach a high enough blood level, they actually stimulate insulin to inhibit lipolysis for the body to get rid of excess ketones and prevent metabolic acidosis. That insulin surge will incidentally shuttle glucose where it needs to go, either in muscle as glycogen or into fat cells, resultantly dropping blood glucose readings. But circulating blood glucose is not a direct measurement of stored muscle glycogen. I don’t see how it could be without taking a sample of muscle and measuring it in a lab.
All that said, I’m not sure if you’re part of the ketogains or optimising nutrition groups on fb, but you have a pretty good grasp of it for the most part. If you want more background knowledge on ketosis and general physiological responses to substrates read Cahill and Frayn’s work. It’s pretty fascinating. And if you want to use keto for body composition, read Lyle’s book. As far as cholesterol goes, Dave Feldman is pretty much the current low carb/keto experimenter as of late, though Peter Attia is also a lipidologist who went low carb, but I haven’t heard much from him.
Fasting glucose levels during extended fasting periods is a good reflection of when stores run out. Simply put, the body is going to replenish muscle stores from organ stores until it starts running out. If the body stores enough glycogen for three days you'd expect to see elevated levels post refeed then a drop after the three day mark - which is exactly what I observed on 3 of 3 occasions so far.
Unless you want to suggest that after three days of fasting dropping glucose levels aren't a biological indicator of stores running out?
I'm suggesting that circulating blood glucose is a direct measurement of circulating blood glucose. How that translates to stored muscle glycogen depletion is completely separate. Liver glycogen freely releases glycogen for blood glucose, but skeletal muscle glycogen exists only to be used by the muscle for anaerobic activity, not released passively.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3248697/
Just as a visual representation, consider that a freeway represents your blood stream, and the cars on that freeway represent blood glucose molecules. When there is little traffic on that freeway, just because there are very few cars does not mean they somehow just disappeared, rather they are stored elsewhere, and in this example, storage is either muscle glycogen or fat cells.
In terms of ketosis induced fasting metabolism on glucose, the basal insulin response due to insulin sensitivity regulates blood glucose levels so a drop in fasting glucose is merely a physiological response to keep it regulated. Hepatic glycogen freely gets depleted during fasting, and I understand what you're trying to convey, but liver glycogen is not muscle glycogen.
https://sci-hub.tw/https://doi.org/10.1016/S0300-595X(76)80028-X
As for direct measurement of skeletal muscle glycogen, biopsies have been the clinical gold standard of glycogen measurement.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5371784/
Regarding the claim you are responding to.
I've never seen where it was found that blood glycogen would be filling muscle stores if the liver also needed topping off.
And as you have mentioned, insulin needs to be up anyway for blood levels being too high.
In other words, I thought liver was given precedence over muscle stores.
Hence the reason the body prefers to keep muscle stores lower than potential during a diet, because what is eaten goes first to liver, then to muscles stores while also being used for energy needs right then.
Hence the reason coming out of a diet usually has water weight increase for this specific reason - potential stores are topped off again.
And of course a slight twist to this in keto, but is muscle stores ever given preference over liver?
Seems like bad survival mechanism.0 -
Muscle biopsy wouldn't be a good measure as glycogen storage is non-uniform distribution. Even if one area was depleted no telling if that means another is...
Some good points. And depletion here being an oversimplification because the body isn't ever going to be truly depleted. In full on ketosis the body still produces enough glycogen for day to day.With refeeds you can completely saturate glycogen in about 2-3 days by eating a buttload of easily digestible carbs and topping off stores in succeeding days. Glycogen depletion occurs when you perform aerobic and total body anaerobic exercise consistently throughout the week while keeping carb intake minimal.
You can replenish glycogen sufficiently in a single day or if you're like me and an amateur competitive eater in a single meal. My latest personal experiments show elevated glucose levels for four days after a re-feed post glycogen depletion (three days fasting).
Glycogen depletion occurs with prolonged caloric deficit and doesn't require exercise for depletion. It also requires both carbohydrate and protein intake reductions as the body can produce substantial glycogen levels from gluconeogensis. My latest personal experiments also show elevated glycogen levels can be maintained on a protein/fat only re-feed for at least three days post glycogen depletion (five days fasting).
Yes, you can replenish glycogen in one day, but the period of not eating slowly dips into liver glycogen, and that period of not eating is sleep. Therefore, you'd have to top it off in the days succeeding day 1.
Liver glycogen depletion occurs with a prolonged caloric deficit. Muscle glycogen doesn't follow that rule. It exists to live for fueling the muscle groups where they reside. Using extended fasting as an example, if you needed to sprint for your life (for whatever reason you want to use), muscle glycogen (and ATP) is used in that process to run like hell.
Gluconeogenesis can replete muscle glycogen in about 18-24 hours after those stores have been used, so to consistently deplete them in preparation for a refeed, you would have to consistently use them. Gluconeogenesis can use any substrate that can be broken down to create carbon, hydrogen, and oxygen molecules.
As for measuring glycogen levels, unless you're taking muscle biopsies and measuring them in a lab, glucose levels only indicate free-floating glucose in the blood, which is not indicative of storage capacity.
For the purposes of a carb refeed, aside from leptin/hormonal regulation, is if you're following CKD, you want to be glycogen depleted from a total body perspective to prime the muscles for an anabolic response to stimulus and that glucose/insulin spike is what's going to be the catalyst for that.
But I'll bite.. what experiments are you running? What's your hypothesis, method, and data from the results you've seen?
But muscular stores run out a bit quicker than you suggest and they are replenished from the body's stores - as mentioned mainly from the liver. Many other energy substrates can be directly consumed such as with the lactic acid shuffle. Cortisol and lactic acid aren't a useless byproduct...
For the experiments mentioned, I was merely testing the ability of protein/fat meals to replenish glycogen stores. In my prior experiments I had a lot of people say gluconeogenesis can't occur to sufficient quantities to replenish stores.
So I fasted for three days, did a carbohydrate re-feed, measured fasting glucose for 5 fasting days to establish a baseline, did a protein/fat only re-feed, then measured glucose over a 4 day fasting period. Crazy enough fasting glucose levels go up (mine around 105 mg/dL on fasted states). While the body is fasted insulin secretion is suppressed to allow the body to transport glycogen stores. Just didn't think it'd be that high... So when it drops below baseline levels I know I am running out of stores. A week long fast will put me at 50 mg/dL.
I do a lot on personal experimentation on cholesterol, fasting glucose, BMR, ketosis, body composition, etc. But that's another story...
Right. Muscle glycogen never gets completely depleted and some do get used upon moderately intense exertion, and protein and fat are sufficient enough to restore muscle glycogen, you’re completely correct, but for those same reasons that they’re effectively constant as they’re replenished by gng, they exist in the muscle to fuel anaerobic activity. The point of glycogen depleting exercise is to use up as much glycogen as possible, typically more than natural replenishment rates, and super compensate glycogen stores.. which in this case, carbs are more effective since they bypass the rate of gng because pure glucose can readily be converted directly to glycogen in the liver.
In ketosis, insulin is suppressed, as you stated, but that also means glucose is spared for parts of the the brain and cells that cannot use ketones or fatty acids as fuel, so in the case of early stages of starvation ketosis (evidenced by extended fasting), gng ramps up to provide glucose for them. When bhb levels reach a high enough blood level, they actually stimulate insulin to inhibit lipolysis for the body to get rid of excess ketones and prevent metabolic acidosis. That insulin surge will incidentally shuttle glucose where it needs to go, either in muscle as glycogen or into fat cells, resultantly dropping blood glucose readings. But circulating blood glucose is not a direct measurement of stored muscle glycogen. I don’t see how it could be without taking a sample of muscle and measuring it in a lab.
All that said, I’m not sure if you’re part of the ketogains or optimising nutrition groups on fb, but you have a pretty good grasp of it for the most part. If you want more background knowledge on ketosis and general physiological responses to substrates read Cahill and Frayn’s work. It’s pretty fascinating. And if you want to use keto for body composition, read Lyle’s book. As far as cholesterol goes, Dave Feldman is pretty much the current low carb/keto experimenter as of late, though Peter Attia is also a lipidologist who went low carb, but I haven’t heard much from him.
Fasting glucose levels during extended fasting periods is a good reflection of when stores run out. Simply put, the body is going to replenish muscle stores from organ stores until it starts running out. If the body stores enough glycogen for three days you'd expect to see elevated levels post refeed then a drop after the three day mark - which is exactly what I observed on 3 of 3 occasions so far.
Unless you want to suggest that after three days of fasting dropping glucose levels aren't a biological indicator of stores running out?
I'm suggesting that circulating blood glucose is a direct measurement of circulating blood glucose. How that translates to stored muscle glycogen depletion is completely separate. Liver glycogen freely releases glycogen for blood glucose, but skeletal muscle glycogen exists only to be used by the muscle for anaerobic activity, not released passively.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3248697/
Just as a visual representation, consider that a freeway represents your blood stream, and the cars on that freeway represent blood glucose molecules. When there is little traffic on that freeway, just because there are very few cars does not mean they somehow just disappeared, rather they are stored elsewhere, and in this example, storage is either muscle glycogen or fat cells.
In terms of ketosis induced fasting metabolism on glucose, the basal insulin response due to insulin sensitivity regulates blood glucose levels so a drop in fasting glucose is merely a physiological response to keep it regulated. Hepatic glycogen freely gets depleted during fasting, and I understand what you're trying to convey, but liver glycogen is not muscle glycogen.
https://sci-hub.tw/https://doi.org/10.1016/S0300-595X(76)80028-X
As for direct measurement of skeletal muscle glycogen, biopsies have been the clinical gold standard of glycogen measurement.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5371784/
You're missing the point that this is during a completely fasted state in which the body is transporting all reserves.
So on that highway imagine no gas stations are open but you have several containers of gas in your trunk. As you run out your car either stops, or you refill the tank with your stores. If you were monitoring your car's fuel lines you can safely assume once the gas started drizzling in you were unable to refill it with stores...
Are you trying to state the body won't deplete reserves during long periods of fasting? Are you suggesting fasting glucose drops to 50 mg/dL with reserves still available?
I linked the Cahill starvation study in my response for you to read and understand why I'm saying what I'm saying. Completely fasted state for days = starvation.
https://sci-hub.tw/https://doi.org/10.1016/S0300-595X(76)80028-X
"Muscle cell glycogen appears to function as an immediate reserve source of available glucose for muscle cells. Other cells that contain small amounts use it locally, as well. As muscle cells lack glucose-6-phosphatase, which is required to pass glucose into the blood, the glycogen they store is available solely for internal use and is not shared with other cells. This is in contrast to liver cells, which, on demand, readily do break down their stored glycogen into glucose and send it through the blood stream as fuel for other organs.[14]"
https://en.wikipedia.org/wiki/Glycogen#Muscle
In your metaphor, those gas containers are fat stores, and to an extent muscle and organ protein act as vessels to break down protein for amino activity. Muscle glycogen is a one way process, meaning it doesn't simply leak out in the face of nutrient deprivation but some of it does get used during the period of normal activity.
Metabolism in ketosis is a survival mechanism to spare as much organ breakdown as possible, primarily the important organs being the brain and life organs.
To @heybales post, you're correct that liver glycogen readily gets preference over muscle at any time, and muscle glycogen isn't saturated to capacity during a deficit or carbohydrate restriction. Reserves are generally enough for limited amounts of anaerobic activity and gluconeogenesis/glycogenesis naturally restores reserve levels.
Either we're all arguing the same thing said differently, or I'm completely off base, but my intention is to distinguish the difference between how muscle glycogen is stored and expended and how circulating blood glucose is not a direct measurement of muscle glycogen stores.4 -
Muscle biopsy wouldn't be a good measure as glycogen storage is non-uniform distribution. Even if one area was depleted no telling if that means another is...
Some good points. And depletion here being an oversimplification because the body isn't ever going to be truly depleted. In full on ketosis the body still produces enough glycogen for day to day.With refeeds you can completely saturate glycogen in about 2-3 days by eating a buttload of easily digestible carbs and topping off stores in succeeding days. Glycogen depletion occurs when you perform aerobic and total body anaerobic exercise consistently throughout the week while keeping carb intake minimal.
You can replenish glycogen sufficiently in a single day or if you're like me and an amateur competitive eater in a single meal. My latest personal experiments show elevated glucose levels for four days after a re-feed post glycogen depletion (three days fasting).
Glycogen depletion occurs with prolonged caloric deficit and doesn't require exercise for depletion. It also requires both carbohydrate and protein intake reductions as the body can produce substantial glycogen levels from gluconeogensis. My latest personal experiments also show elevated glycogen levels can be maintained on a protein/fat only re-feed for at least three days post glycogen depletion (five days fasting).
Yes, you can replenish glycogen in one day, but the period of not eating slowly dips into liver glycogen, and that period of not eating is sleep. Therefore, you'd have to top it off in the days succeeding day 1.
Liver glycogen depletion occurs with a prolonged caloric deficit. Muscle glycogen doesn't follow that rule. It exists to live for fueling the muscle groups where they reside. Using extended fasting as an example, if you needed to sprint for your life (for whatever reason you want to use), muscle glycogen (and ATP) is used in that process to run like hell.
Gluconeogenesis can replete muscle glycogen in about 18-24 hours after those stores have been used, so to consistently deplete them in preparation for a refeed, you would have to consistently use them. Gluconeogenesis can use any substrate that can be broken down to create carbon, hydrogen, and oxygen molecules.
As for measuring glycogen levels, unless you're taking muscle biopsies and measuring them in a lab, glucose levels only indicate free-floating glucose in the blood, which is not indicative of storage capacity.
For the purposes of a carb refeed, aside from leptin/hormonal regulation, is if you're following CKD, you want to be glycogen depleted from a total body perspective to prime the muscles for an anabolic response to stimulus and that glucose/insulin spike is what's going to be the catalyst for that.
But I'll bite.. what experiments are you running? What's your hypothesis, method, and data from the results you've seen?
But muscular stores run out a bit quicker than you suggest and they are replenished from the body's stores - as mentioned mainly from the liver. Many other energy substrates can be directly consumed such as with the lactic acid shuffle. Cortisol and lactic acid aren't a useless byproduct...
For the experiments mentioned, I was merely testing the ability of protein/fat meals to replenish glycogen stores. In my prior experiments I had a lot of people say gluconeogenesis can't occur to sufficient quantities to replenish stores.
So I fasted for three days, did a carbohydrate re-feed, measured fasting glucose for 5 fasting days to establish a baseline, did a protein/fat only re-feed, then measured glucose over a 4 day fasting period. Crazy enough fasting glucose levels go up (mine around 105 mg/dL on fasted states). While the body is fasted insulin secretion is suppressed to allow the body to transport glycogen stores. Just didn't think it'd be that high... So when it drops below baseline levels I know I am running out of stores. A week long fast will put me at 50 mg/dL.
I do a lot on personal experimentation on cholesterol, fasting glucose, BMR, ketosis, body composition, etc. But that's another story...
Right. Muscle glycogen never gets completely depleted and some do get used upon moderately intense exertion, and protein and fat are sufficient enough to restore muscle glycogen, you’re completely correct, but for those same reasons that they’re effectively constant as they’re replenished by gng, they exist in the muscle to fuel anaerobic activity. The point of glycogen depleting exercise is to use up as much glycogen as possible, typically more than natural replenishment rates, and super compensate glycogen stores.. which in this case, carbs are more effective since they bypass the rate of gng because pure glucose can readily be converted directly to glycogen in the liver.
In ketosis, insulin is suppressed, as you stated, but that also means glucose is spared for parts of the the brain and cells that cannot use ketones or fatty acids as fuel, so in the case of early stages of starvation ketosis (evidenced by extended fasting), gng ramps up to provide glucose for them. When bhb levels reach a high enough blood level, they actually stimulate insulin to inhibit lipolysis for the body to get rid of excess ketones and prevent metabolic acidosis. That insulin surge will incidentally shuttle glucose where it needs to go, either in muscle as glycogen or into fat cells, resultantly dropping blood glucose readings. But circulating blood glucose is not a direct measurement of stored muscle glycogen. I don’t see how it could be without taking a sample of muscle and measuring it in a lab.
All that said, I’m not sure if you’re part of the ketogains or optimising nutrition groups on fb, but you have a pretty good grasp of it for the most part. If you want more background knowledge on ketosis and general physiological responses to substrates read Cahill and Frayn’s work. It’s pretty fascinating. And if you want to use keto for body composition, read Lyle’s book. As far as cholesterol goes, Dave Feldman is pretty much the current low carb/keto experimenter as of late, though Peter Attia is also a lipidologist who went low carb, but I haven’t heard much from him.
Fasting glucose levels during extended fasting periods is a good reflection of when stores run out. Simply put, the body is going to replenish muscle stores from organ stores until it starts running out. If the body stores enough glycogen for three days you'd expect to see elevated levels post refeed then a drop after the three day mark - which is exactly what I observed on 3 of 3 occasions so far.
Unless you want to suggest that after three days of fasting dropping glucose levels aren't a biological indicator of stores running out?
I'm suggesting that circulating blood glucose is a direct measurement of circulating blood glucose. How that translates to stored muscle glycogen depletion is completely separate. Liver glycogen freely releases glycogen for blood glucose, but skeletal muscle glycogen exists only to be used by the muscle for anaerobic activity, not released passively.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3248697/
Just as a visual representation, consider that a freeway represents your blood stream, and the cars on that freeway represent blood glucose molecules. When there is little traffic on that freeway, just because there are very few cars does not mean they somehow just disappeared, rather they are stored elsewhere, and in this example, storage is either muscle glycogen or fat cells.
In terms of ketosis induced fasting metabolism on glucose, the basal insulin response due to insulin sensitivity regulates blood glucose levels so a drop in fasting glucose is merely a physiological response to keep it regulated. Hepatic glycogen freely gets depleted during fasting, and I understand what you're trying to convey, but liver glycogen is not muscle glycogen.
https://sci-hub.tw/https://doi.org/10.1016/S0300-595X(76)80028-X
As for direct measurement of skeletal muscle glycogen, biopsies have been the clinical gold standard of glycogen measurement.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5371784/
You're missing the point that this is during a completely fasted state in which the body is transporting all reserves.
So on that highway imagine no gas stations are open but you have several containers of gas in your trunk. As you run out your car either stops, or you refill the tank with your stores. If you were monitoring your car's fuel lines you can safely assume once the gas started drizzling in you were unable to refill it with stores...
Are you trying to state the body won't deplete reserves during long periods of fasting? Are you suggesting fasting glucose drops to 50 mg/dL with reserves still available?
I linked the Cahill starvation study in my response for you to read and understand why I'm saying what I'm saying. Completely fasted state for days = starvation.
https://sci-hub.tw/https://doi.org/10.1016/S0300-595X(76)80028-X
"Muscle cell glycogen appears to function as an immediate reserve source of available glucose for muscle cells. Other cells that contain small amounts use it locally, as well. As muscle cells lack glucose-6-phosphatase, which is required to pass glucose into the blood, the glycogen they store is available solely for internal use and is not shared with other cells. This is in contrast to liver cells, which, on demand, readily do break down their stored glycogen into glucose and send it through the blood stream as fuel for other organs.[14]"
https://en.wikipedia.org/wiki/Glycogen#Muscle
In your metaphor, those gas containers are fat stores, and to an extent muscle and organ protein act as vessels to break down protein for amino activity. Muscle glycogen is a one way process, meaning it doesn't simply leak out in the face of nutrient deprivation but some of it does get used during the period of normal activity.
Metabolism in ketosis is a survival mechanism to spare as much organ breakdown as possible, primarily the important organs being the brain and life organs.
To @heybales post, you're correct that liver glycogen readily gets preference over muscle at any time, and muscle glycogen isn't saturated to capacity during a deficit or carbohydrate restriction. Reserves are generally enough for limited amounts of anaerobic activity and gluconeogenesis/glycogenesis naturally restores reserve levels.
Either we're all arguing the same thing said differently, or I'm completely off base, but my intention is to distinguish the difference between how muscle glycogen is stored and expended and how circulating blood glucose is not a direct measurement of muscle glycogen stores.
And along those lines... As a type 1 diabetic, I can absolutely attest that my blood sugar will plummet to 50 or below, without actually bothering to tap into its reserves. Those reserves will kick in after time, but in people like me, it's not an automatic response. The insulin has done such a fantastic job of doing its job, that it's too fast a reaction for the alpha cells to release glucagon to tell the liver to release the glycogen.
In me, it becomes more challenging, for example, because I have no alpha cell response. So my liver will kick out the glycogen *late* after it's realized that OH HAI WE HAVE A THING THAT IS CREATING EPINEPHRINE AND WE NEED TO RESPOND TO THAT. Which is why I'll get stuck with a rebound high. Because the liver doesn't realize that the event has passed, and the glycogen isn't need anymore.
Now, conversely, and perhaps in more of a "it all can happen" sort of thing, I will get stuck in these cycles where, since my default is to have pretty low glycogen stores, I will not be able to break out of a cycle of hypos. So then, I'll have these lows, treat them, and have another serious low the next day.4 -
*waves again*
Gawd, not even managing to keep up with my own thread! Been busy, busy, busy going into the city to identify bird bones for the past week and a half. Last day today, yay!!! Then once that data is entered, it's time to write. But I should have a bit more online time as of next week, because I won't have the up to 3 hours of travel on top of my normal work hours.7 -
collectingblues wrote: »Nony_Mouse wrote: »I've finally read nearly all of this thread. But I need people to dumb things down for me.
@Nony_Mouse Why are you now doing "moderately low carb"? I must admit I cringe at the thought of one of my heroes going the low carb cult route, but knowing you, you will have a good reason.
I've always eaten lowish carb (around 100-120) at a deficit, not because I think there's any magic in it, just because it's easier for me to create and sustain a deficit that way. Even at maintenance 150g a day would be the norm for me most of the time. I'm all about the protein, and the things I eat tend to be higher fat (I'm looking at you, avocado and halloumi, oh and dark choc pb in my shakes!), so by the time those two things are in there's not a lot of room left for carbs, and they're the thing I care least about. Nothing cultish about it, just basic maths. I just don't shout it from the rooftops that I'm technically low carb (if you subscribe to that meaning lower than 150g), because it's just the way I eat. Dropped that a little lower than normal the past few days simply to shift some of the unholy amount of water weight I was lugging around. Purely psychological, I know it isn't fat weight.
So there you go, I've always been moderately low carb, you just didn't know it
I've been doing the same thing, Nony. The dietitian had me doing a moderate low carb during the pre-race taper, to try to curb that taper weight gain and keep my brain from freaking out. I actually enjoyed it, and found it easier to do when I was focusing on protein more, so it seems to have stuck.
*slowly raises hand* I'm also low to moderate carb right now, just because that's how the macros land when I focus on protein. I would actually prefer to be higher carb since I'm ramping up my cycling and running, but I seem to be unconsciously reaching for the protein, fat and fiber trifecta.
Me, too. I've been really good at managing my macros for the last couple of months for roughly a 1/3 for each. My exercise has been crap for the last few weeks (though still getting steps) because of the 15 hour work days. But I keeping on track with what I can. I keep lots of food in my office, so even when there are emergency meetings, I can still manage my nutrition--at least the macros.1 -
I'll interject too the studies that show when you enter exercising state, despite increase glucose usage, the required amount is not all pulled from muscle stores, blood sugar is used too.
This is the misunderstanding at the start of aerobic workouts for the first 10-30 min depending on how well trained you are.
Blood sugar contributes a decent initial amount, lowering the longer you go and using the muscle stores more.
At the same time, the ratio of fat/carbs as source starts higher glucose then it'll end up later, again depending on training and warmup.
So double whammy to liver stores at the start of exercise. Even if keto adapted. Not a huge amount, but a difference.3 -
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Right. I think we can at least agree that glucose is readily available fuel for immediate use by whatever system needs it.
Glycogen as a storage bundle of glucose, will be freely released from the liver to provide more glucose as needs are increased. During intense glycolytic activity muscle glycogen provides glucose for muscles.
https://www.ncbi.nlm.nih.gov/books/NBK22417/
There is never a point in time where we don’t have blood glucose circulation otherwise we’d die.4 -
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And perhaps a slightly more digestible version of metabolism during starvation:
https://www.patreon.com/posts/17710895
Full text:
Bill Lagakos posted
Glucose dynamics during prolonged fasts
This is a somewhat complicated level of metabolism. Which tissues are producing what & how much, what are they burning & how much, etc., etc...
After a few weeks, things begin to level out -- we'll pick it up there. Much of this is from a class I TA'd for in grad school, this book, and all the Cahill studies.
"The rate of glucose use at this time is around 90-100 g per day [remember, this is starvation, so all of that glucose comes from gluconeogenesis]. Of that, about 40 g is recycled via the Cori and glucose-alanine cycles and the remainder is 'new' glucose, ~18 g from glycerol and ~45 g from amino acids."
http://caloriesproper.com/wp-content/uploads/2018/03/Screenshot-2018-03-16-at-3.43.02-PM.png
"To maintain this rate of proteolysis (supplying amino acids for gluconeogenesis) would still require the breakdown of about 100 g protein (amino acids) per day."
"The glucose-sparing effect of fat-derived fuels" should more accurately be called "the muscle-sparing effect of fat-derived fuels."
http://caloriesproper.com/wp-content/uploads/2018/03/Screenshot-2018-03-16-at-3.40.13-PM.png
"However, as ketones continue to rise (up to >5 mM), brain can use them in place of much of its glucose utilization. Brain ketone use is driven by substrate supply, but there is evidence that the ketone body transporters in brain increase during starvation. The brain still requires some glucose but it appears to restrict metabolism of most the glucose it uses via glycolysis to lactate, with very little undergoing complete oxidation to CO2 (we're really trying to "spare glucose"). Of course the glycolytic tissues continue to recycle glucose. The lactate goes back to liver for gluconeogenesis.
Most other tissues are using fatty acids or ketones except skeletal muscle, which uses predominantly fatty acids but we don’t know why – perhaps it is to spare ketones for the brain (although circulating ketone levels don't further increase).
Plasma glucose use has now decreased to about 1-2 g per hour, half for glycolysis and half for oxidation to CO2, ie, 24 g oxidized per day.
The high levels of ketone bodies can be considered as a water-soluble fuel for the brain to use in place of glucose. However, they come with a price, they are strong acids and produce a metabolic "starvation acidosis." They are also freely filtered in the kidney; this means that as ketones, rise they will be lost in the urine (a loss of energy in starvation = no bueno) and this must be buffered. Remember we excrete such strong acids as ammonium salts and the ammonia comes from glutamine metabolism in the kidney. Glutamine arises from the extensive proteolysis in muscle and is utilized by the kidney to produce ammonia, bicarbonate, and glucose. Thus renal gluconeogeneis increases in long term starvation and is directly related to the control of acidosis. It is often stated that in prolonged starvation, kidney gluconeogenesis is more important than that in liver; however, by this time the rate of gluconeogenesis in liver has decreased considerably. In keeping with this switch in gluconeogenesis tissue there is a change in nitrogen excretion. Initially during starvation urea excretion increases (reflecting the increased protein breakdown to provide gluconeogenic substrate) but then urea decreases and ammonia excretion increases as ketoacidosis develops. In long-term starvation urea only accounts for about 1 g of nitrogen excreted per day while ammonia accounts for >3 g (compared to 15 g and 1 g respectively at day one of starvation)."
TO BE CONTINUED!1
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