So confused. How does your body actually lose fat?
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canadianlbs wrote: »fromnebraska wrote: »So why are people bothering with this crazy keto thing if they can lose weight by eating a large variety of foods?
the only guy i know well who eats keto is still doing it and still really happy with it after more than a year. fwiw, he's been 'obese' [but very strong] all the years i've known him, and he simply says keto is the only 'diet' he's ever undertaken that feels 'natural' to him.
that doesn't mean it would be natural to anyone else. for whatever reason, the macro lineup in keto is just sustainable for him. he's in his late thirties and says it's the first time he's ever successfully stayed in a deficit without hunger and cravings defeating him.
doesn't mean he wouldn't lose weight on a non-keto diet. he's done that too, and it's worked too. but the way he put it the last time he talked about it was 'sure, but why would i want to be miserable for the rest of my life if i didn't need to?' for (again) whatever reason, keto is the way of eating that makes him non-miserable.
I think that’s the key. Finding a diet that you can stick with long term, not a diet that promises you will burn fat faster.
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fromnebraska wrote: »Thanks everyone! That was very helpful. I was thinking incorrectly about the keto diet burning most body fat vs dietary fat.
The other part that is confusing to their claims is the misnomer that unless doing keto, you are burning mainly or only carbs, no fat is insinuated by some.
Except for the 2-4 hrs after a meal (depend on size and carb/prot load of it), and up into higher levels of activity and exercise - your body is mainly burning fat for fuel anyway all day long.
As you go higher intensity for exercise - more carbs is source of fuel. Keto doesn't change that fact.
Except your brain - which is burning glucose (carbs) in average meals.
Keto just has your brain burning ketones instead, so there's that little extra bit of fat.
And then to stay in keto, your insulin isn't rising as much since not eating as many carbs (though protein elevates insulin too) - so not as long after a meal are your insulin levels dropping, and fat burning from stored fat occurs again.
While insulin is raised - you are burning what you ate, and carbs going off to restore liver and muscle stores and be used as energy source, protein going off for repairs, fat is being burned or stored since fat storage turned on.
All a diet does is having you eating less so that insulin never stays up as long as it does when not in a diet.
So not in a diet a meal may have insulin up and fat release from cells turned off for 2-4 hrs say.
In a diet it may be 1-3 hrs instead - so an extra hour of fat burning daily from your cells, after each meal.
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fromnebraska wrote: »Thanks everyone! That was very helpful. I was thinking incorrectly about the keto diet burning most body fat vs dietary fat.
The other part that is confusing to their claims is the misnomer that unless doing keto, you are burning mainly or only carbs, no fat is insinuated by some.
Except for the 2-4 hrs after a meal (depend on size and carb/prot load of it), and up into higher levels of activity and exercise - your body is mainly burning fat for fuel anyway all day long.
As you go higher intensity for exercise - more carbs is source of fuel. Keto doesn't change that fact.
Except your brain - which is burning glucose (carbs) in average meals.
Keto just has your brain burning ketones instead, so there's that little extra bit of fat.
And then to stay in keto, your insulin isn't rising as much since not eating as many carbs (though protein elevates insulin too) - so not as long after a meal are your insulin levels dropping, and fat burning from stored fat occurs again.
While insulin is raised - you are burning what you ate, and carbs going off to restore liver and muscle stores and be used as energy source, protein going off for repairs, fat is being burned or stored since fat storage turned on.
All a diet does is having you eating less so that insulin never stays up as long as it does when not in a diet.
So not in a diet a meal may have insulin up and fat release from cells turned off for 2-4 hrs say.
In a diet it may be 1-3 hrs instead - so an extra hour of fat burning daily from your cells, after each meal.
I think you are over complicating this.
Your body has certain calorie needs to survive and do the activity you do.
You eat food with a certain calorie content and your body can burn this or store this. Your body is real good at extracting energy from protein, fat or carbs. It tends to burn the stuff it can store less of. So it burns carbs and protein for energy in preference to say fat. This really doesn't matter though because it's internal juggling of the body.
Now if your output energy exceeds your input energy the body must burn stored calories to make up the difference.
It has limited supplies of protein (amino acids in the blood and your muscles) and carbohydrates (glycogen and blood sugar). It has huge stores of fat to burn.
So short term in a deficit of calories you might use up your glycogen etc but after a week or so it just has to come from fat. You will get some lean tissue loss based on how severer your deficit is and how much exercise you do but really in the end the only massive source of calories is fat.
So you stay in a deficit for long enough and the fat will go. Now it won't go fast because fat has a lot of calories.
So if you eat at a deficit, thermodynamics says you must loose fat. It's a guarantee. Obviously this is a real deficit and not some pretend one where you don't count all you eat or cheat etc.
People get confused by the internal juggling the body does. Say for example burning carbs in preference to fat but in the end it must burn fat to get the calories if the energy deficit is continuous.
Your body will adapt to the macro nutrients you eat but that's just the bodies way of extracting the maximum energy and matching usage rate to intake. So eating more fat eventually makes your muscles adapt to burn free fatty acids directly but that's just to keep you running etc at the rate you want with the food source it has available. It doesn't change the thermodynamics.
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fromnebraska wrote: »Thanks everyone! That was very helpful. I was thinking incorrectly about the keto diet burning most body fat vs dietary fat.
The other part that is confusing to their claims is the misnomer that unless doing keto, you are burning mainly or only carbs, no fat is insinuated by some.
Except for the 2-4 hrs after a meal (depend on size and carb/prot load of it), and up into higher levels of activity and exercise - your body is mainly burning fat for fuel anyway all day long.
As you go higher intensity for exercise - more carbs is source of fuel. Keto doesn't change that fact.
Except your brain - which is burning glucose (carbs) in average meals.
Keto just has your brain burning ketones instead, so there's that little extra bit of fat.
And then to stay in keto, your insulin isn't rising as much since not eating as many carbs (though protein elevates insulin too) - so not as long after a meal are your insulin levels dropping, and fat burning from stored fat occurs again.
While insulin is raised - you are burning what you ate, and carbs going off to restore liver and muscle stores and be used as energy source, protein going off for repairs, fat is being burned or stored since fat storage turned on.
All a diet does is having you eating less so that insulin never stays up as long as it does when not in a diet.
So not in a diet a meal may have insulin up and fat release from cells turned off for 2-4 hrs say.
In a diet it may be 1-3 hrs instead - so an extra hour of fat burning daily from your cells, after each meal.
Now if your output energy exceeds your input energy the body must burn stored calories to make up the difference.
It has limited supplies of protein (amino acids in the blood and your muscles) and carbohydrates (glycogen and blood sugar). It has huge stores of fat to burn.
So short term in a deficit of calories you might use up your glycogen etc but after a week or so it just has to come from fat. You will get some lean tissue loss based on how severer your deficit is and how much exercise you do but really in the end the only massive source of calories is fat.
So you stay in a deficit for long enough and the fat will go. Now it won't go fast because fat has a lot of calories.
So if you eat at a deficit, thermodynamics says you must loose fat. It's a guarantee. Obviously this is a real deficit and not some pretend one where you don't count all you eat or cheat etc.
People get confused by the internal juggling the body does. Say for example burning carbs in preference to fat but in the end it must burn fat to get the calories if the energy deficit is continuous.
Your body will adapt to the macro nutrients you eat but that's just the bodies way of extracting the maximum energy and matching usage rate to intake. So eating more fat eventually makes your muscles adapt to burn free fatty acids directly but that's just to keep you running etc at the rate you want with the food source it has available. It doesn't change the thermodynamics.
Unless you are eating barely any carbs (or no excess protein to be converted to carbs) - you aren't going to use up all your glycogen stores such that fat is all that is remaining and all that can be used or preferred to be used.
You use fat every day as energy source, vast majority of day, and depending on amount eaten and length insulin is elevated, possibly majority of it as energy source too.
Where is it burning carbs in preference to fat going to happen for the scenario you setup - it doesn't unless you want to include intense exercise.
Ask to see anyone's metabolic test where they give them actual results of % of energy source, or anyone that has done a VO2max test - or go look up the many examples that are online.
This misunderstanding that fat is NOT the primary fuel in the first place confounds me.
You must keep ramping up your activity level to pretty decent intensity to even start burning a majority of carbs as energy source.
And your body is most certainly not "matching the usage rate to intake".
If that was the fact - no one would get fat.
What is the difference for non-keto diet bodies burning upwards of 90% fat during majority of day, compared to keto-adapted and this "muscles adapt to burn free fatty acids directly" I'll see keto advocates claim?
What is my body burning here exactly with fat as energy source right now then?
Here's 20 sec worth of resting prior to my VO2max test.
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fromnebraska wrote: »Thanks everyone! That was very helpful. I was thinking incorrectly about the keto diet burning most body fat vs dietary fat.
The other part that is confusing to their claims is the misnomer that unless doing keto, you are burning mainly or only carbs, no fat is insinuated by some.
Except for the 2-4 hrs after a meal (depend on size and carb/prot load of it), and up into higher levels of activity and exercise - your body is mainly burning fat for fuel anyway all day long.
As you go higher intensity for exercise - more carbs is source of fuel. Keto doesn't change that fact.
Except your brain - which is burning glucose (carbs) in average meals.
Keto just has your brain burning ketones instead, so there's that little extra bit of fat.
And then to stay in keto, your insulin isn't rising as much since not eating as many carbs (though protein elevates insulin too) - so not as long after a meal are your insulin levels dropping, and fat burning from stored fat occurs again.
While insulin is raised - you are burning what you ate, and carbs going off to restore liver and muscle stores and be used as energy source, protein going off for repairs, fat is being burned or stored since fat storage turned on.
All a diet does is having you eating less so that insulin never stays up as long as it does when not in a diet.
So not in a diet a meal may have insulin up and fat release from cells turned off for 2-4 hrs say.
In a diet it may be 1-3 hrs instead - so an extra hour of fat burning daily from your cells, after each meal.
I think you are over complicating this.
Your body has certain calorie needs to survive and do the activity you do.
You eat food with a certain calorie content and your body can burn this or store this. Your body is real good at extracting energy from protein, fat or carbs. It tends to burn the stuff it can store less of. So it burns carbs and protein for energy in preference to say fat. This really doesn't matter though because it's internal juggling of the body.
Now if your output energy exceeds your input energy the body must burn stored calories to make up the difference.
It has limited supplies of protein (amino acids in the blood and your muscles) and carbohydrates (glycogen and blood sugar). It has huge stores of fat to burn.
So short term in a deficit of calories you might use up your glycogen etc but after a week or so it just has to come from fat. You will get some lean tissue loss based on how severer your deficit is and how much exercise you do but really in the end the only massive source of calories is fat.
So you stay in a deficit for long enough and the fat will go. Now it won't go fast because fat has a lot of calories.
So if you eat at a deficit, thermodynamics says you must loose fat. It's a guarantee. Obviously this is a real deficit and not some pretend one where you don't count all you eat or cheat etc.
People get confused by the internal juggling the body does. Say for example burning carbs in preference to fat but in the end it must burn fat to get the calories if the energy deficit is continuous.
Your body will adapt to the macro nutrients you eat but that's just the bodies way of extracting the maximum energy and matching usage rate to intake. So eating more fat eventually makes your muscles adapt to burn free fatty acids directly but that's just to keep you running etc at the rate you want with the food source it has available. It doesn't change the thermodynamics.
No - you are very confused about substrate usage, I get the impression you think carbs are used first and fat isn't burned until carbs are depleted. That's simply wrong.
When I did my VO2 max ramp test they analyse your breath which accurately tells you your fuel usage - Respiratory Exchange Ratio.
You start off pedalling slowly and the intensity ramps up steadily - I was (as everyone would be...) using majority of fat with some carbs to begin with, it wasn't until I got to what would be into zone 3 (tempo) pace that I hit the point at which I was burning 50/50 carbs and fat.
Remember that's under exercise conditions. When sleeping or inactive you are running on fat for the vast majority of the time.
Suggest you watch the Layne Norton videos posted on page 3 - they are very informative.3 -
Unless you are eating barely any carbs (or no excess protein to be converted to carbs) - you aren't going to use up all your glycogen stores such that fat is all that is remaining and all that can be used or preferred to be used.
This isn't true. In my first week using MFP my weight dropped by 7lbs and I started to see I was often in ketosis. I was consuming some 130g of carbs / day with 38g of that fiber. That would not even be classified as a low carb diet. In order to enter ketosis the determining factor would be depletion of liver glycogen. So I was depleted. I was weight training about 4 days a week and this I guess was enough to deplete the glycogen.You use fat every day as energy source, vast majority of day, and depending on amount eaten and length insulin is elevated, possibly majority of it as energy source too.
I am not claiming you are not using fat. I am just claiming that the body can adapt in a high fat, low carb diet to burn more fat and burn it more directly.Where is it burning carbs in preference to fat going to happen for the scenario you setup - it doesn't unless you want to include intense exercise.
If carbs are present in the bloodstream in excess and also free fatty acids in excess I am saying that the body will burn the carbs in preference because it has a hard time storing carbs beyond glycogen. Are you not suggesting that if I eat a very large amount of carbs and fats at the same time I would continue to burn the same amount of fat? If that was the case then the body would end up having to make fat from carbs and that's inefficient. What we actually expect to happen is the body shifts to burning more carbs and storing the fat.This misunderstanding that fat is NOT the primary fuel in the first place confounds me.
I am not saying it isn't.You must keep ramping up your activity level to pretty decent intensity to even start burning a majority of carbs as energy source.
Ingesting carbs though reduces the level of fat oxidation. So exercise intensity is not the only thing determining fat and carb usage.And your body is most certainly not "matching the usage rate to intake".
If that was the fact - no one would get fat.
I haven't said the body adjusts to get rid of excess calories!!!! Let me explain what I meant by the 'matching usage rate to intake':
If you eat a low carb diet and exercise at first your body isn't burning as much free fatty acids in the muscles as it it capable of. So to sustain exercise the body makes ketones (from fat) and glucose (from glycerine from fat and protein) and the muscles consume some of this. After a delay of many days it seems the body adapts and a bunch of tissues start being able to burn more free fatty acids directly so ketones and glucose usage decline. The body is matching substrate burning by the muscles with what your eating (fat).What is the difference for non-keto diet bodies burning upwards of 90% fat during majority of day, compared to keto-adapted and this "muscles adapt to burn free fatty acids directly" I'll see keto advocates claim?
Lyle has the breakdown of usage over time on low carb:
'Within 10 hours after the last carbohydrate containing meal, roughly 50% of the body’s total energy
requirements are being met by free fatty acids (FFA).'
'Measurements of fuel use show that approximately 90% of the body’s total fuel
requirements are being met by FFA and ketones by the third day (20). After three weeks of
starvation, the body may derive 93% of its fuel from FFA (10, 21).'
'While muscle initially derives up to 50% of its energy
requirements from ketones (22), this drops to 4-6% by the third week of ketosis. (22, 23).'
Lyle here says that starvation and low carb are essentially the same.What is my body burning here exactly with fat as energy source right now then?
I am unsure what the miss match here is. I don't know anything about vo2max.
I see other places giving figures of ~50% fat oxidation during rest. Not the 90% you say. For example:
http://www.clinicalnutritionespen.com/article/S1751-4991(11)00006-0/fulltext
The average resting RQ of 0.82 thus reflects that the human body derives more than half of its energy from fatty acids and most of the rest from glucose (Table 1).'
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Unless you are eating barely any carbs (or no excess protein to be converted to carbs) - you aren't going to use up all your glycogen stores such that fat is all that is remaining and all that can be used or preferred to be used.
This isn't true. In my first week using MFP my weight dropped by 7lbs and I started to see I was often in ketosis. I was consuming some 130g of carbs / day with 38g of that fiber. That would not even be classified as a low carb diet. In order to enter ketosis the determining factor would be depletion of liver glycogen. So I was depleted. I was weight training about 4 days a week and this I guess was enough to deplete the glycogen.You use fat every day as energy source, vast majority of day, and depending on amount eaten and length insulin is elevated, possibly majority of it as energy source too.
I am not claiming you are not using fat. I am just claiming that the body can adapt in a high fat, low carb diet to burn more fat and burn it more directly.Where is it burning carbs in preference to fat going to happen for the scenario you setup - it doesn't unless you want to include intense exercise.
If carbs are present in the bloodstream in excess and also free fatty acids in excess I am saying that the body will burn the carbs in preference because it has a hard time storing carbs beyond glycogen. Are you not suggesting that if I eat a very large amount of carbs and fats at the same time I would continue to burn the same amount of fat? If that was the case then the body would end up having to make fat from carbs and that's inefficient. What we actually expect to happen is the body shifts to burning more carbs and storing the fat.This misunderstanding that fat is NOT the primary fuel in the first place confounds me.
I am not saying it isn't.You must keep ramping up your activity level to pretty decent intensity to even start burning a majority of carbs as energy source.
Ingesting carbs though reduces the level of fat oxidation. So exercise intensity is not the only thing determining fat and carb usage.And your body is most certainly not "matching the usage rate to intake".
If that was the fact - no one would get fat.
I haven't said the body adjusts to get rid of excess calories!!!! Let me explain what I meant by the 'matching usage rate to intake':
If you eat a low carb diet and exercise at first your body isn't burning as much free fatty acids in the muscles as it it capable of. So to sustain exercise the body makes ketones (from fat) and glucose (from glycerine from fat and protein) and the muscles consume some of this. After a delay of many days it seems the body adapts and a bunch of tissues start being able to burn more free fatty acids directly so ketones and glucose usage decline. The body is matching substrate burning by the muscles with what your eating (fat).What is the difference for non-keto diet bodies burning upwards of 90% fat during majority of day, compared to keto-adapted and this "muscles adapt to burn free fatty acids directly" I'll see keto advocates claim?
Lyle has the breakdown of usage over time on low carb:
'Within 10 hours after the last carbohydrate containing meal, roughly 50% of the body’s total energy
requirements are being met by free fatty acids (FFA).'
'Measurements of fuel use show that approximately 90% of the body’s total fuel
requirements are being met by FFA and ketones by the third day (20). After three weeks of
starvation, the body may derive 93% of its fuel from FFA (10, 21).'
'While muscle initially derives up to 50% of its energy
requirements from ketones (22), this drops to 4-6% by the third week of ketosis. (22, 23).'
Lyle here says that starvation and low carb are essentially the same.What is my body burning here exactly with fat as energy source right now then?
I am unsure what the miss match here is. I don't know anything about vo2max.
I see other places giving figures of ~50% fat oxidation during rest. Not the 90% you say. For example:
http://www.clinicalnutritionespen.com/article/S1751-4991(11)00006-0/fulltext
The average resting RQ of 0.82 thus reflects that the human body derives more than half of its energy from fatty acids and most of the rest from glucose (Table 1).'
Last link - page does not exist. Can't see to comment on what they were looking at.
My comment about VO2max only had to do with where the data came from - the info has nothing to do with VO2max - you don't need to know anything about VO2max at least.
Even the cardiac heart muscle as a constant fast acting muscle uses fat, which may surprise some considering other muscle used in such a manner would likely be high glucose usage.
https://www.ncbi.nlm.nih.gov/books/NBK22436/
To your observation of being in ketosis - the liver must not be drained for body to do that - merely low enough it feels the need. This also doesn't speak to your muscle glucose stores which cannot be put back into the bloodstream for general use - it's dedicated to muscle usage once there.
When blood glucose levels are up after eating, and insulin goes up to bring it down - use as energy source is not the only place it's going - it's going to those muscle stores and liver stores.
It's used somewhat for energy source right then right along with available fat from what was already there and what is eaten. No need for conversion to fat yet unless everything else is topped off and blood sugar has remained high too long.
Insulin also gets the protein off where it is desired most - which isn't fuel source (just putting that in since many think it is).
The rate of elevated blood glucose used as energy source has been seen to be variable - depends on how much muscle and liver stores need to be refilled. Your example of low carb eating and lifting - that extra blood sugar shuttled right off to muscle stores probably and insulin drops right back down.
The body adapting to burn more fat is mainly the difference between the burning of glucose by brain to ketones.
No other functions that already used fat are suddenly going to start burning more just because more is available.
The amount of energy the brain needs doesn't change (around 350-450 cal/day) - the source does in keto state.
The relative inefficiency of that source is now the extra fat you are burning.
Glucose easy, no conversions needed. Ketones less efficient, wasted energy in conversion, tad more fat burned.
I'd have to go find some older sources for that difference. It ain't great.
And frankly considering the energy required to store glucose and release it, and water management along with it, is now gone, I wonder how much an increase it is. That action has an energy cost to it also.
As to the body burning more fat as intensity ramps up - that barely has been shown to happen in studies.
Usually when exercise starts the body is using higher level of glucose to fat, after about 20 min it's settled into whatever ratio it needs.
So there fat-adapted (and fasted aerobic training can cause this ability too actually) means you start out with the same ratio you'd end up with.
So to @sijomial comment about 50% up at tempo pace - if he held that pace for 20 min, the actual ratio slowly change to say 40% carbs/60% fat. (Actually for his aerobic trained body - probably 5 min in reality.)
So for avg person for 20 min you have a tad extra fat burn compared to otherwise.
500 cal/hr workout say, 60% fat = 300/hr or 75 for first 15 min, keto-adapted say 70% = 350/hr or 87.5 for first 15 min.
Keto adapted burned extra 12.5 calories in fat instead of carbs.
But in the balance of the day - this would be meaningless because you aren't burning more, just different source.
As to ingesting carbs changing all that - yes indeed, but blood sugar drops even faster then as some shuttled off to muscles for storage and some used at higher rate.
Ingested during the workout - studies have shown it doesn't change the ratio. Body can only absorb so much from the gut in the first place
It appears Lyle's comments are about the switch over to keto state.
And the fact of less insulin spikes shutting off fat release from the cells while elevated, does indeed mean more free-fatty acids available for use.
I don't know what his 10 hrs is about - people getting the metabolic tests don't have to wait that long after eating last meal to show that same upwards of 90% fat use. 4-5 hrs shows that drop under normal circumstances.
Perhaps he is being specific to type of fat being used.
But even Lyle acknowledges in his online writings that there isn't some inherent change or benefit to keto above other diets that makes it magically do something special.
What he does acknowledge is that your intensity at some types of workouts has a great chance of being lowered.
Oh, the rate of creating glucose from non-glucose sources is WAY too slow for use by the muscles in any actual need during exercise.
If you are actually at an intensity that requires glucose at probably above 10% - it's used faster than it could ever be created.
This is the true "wall" of marathoning or "bonk" of cycling. Lactic acid and other sources are just too slow and too low quantity to be meaningful - so the body slows way down to instead meet the ability for aerobic fat burning to supply what's needed.
This is basically a crawl or fall off the bike at this point since that is rather slow. Of course as this point other issues have usually presented too, electrolyte imbalance, muscle cramping, low blood sugar so impaired thinking (which likely occurred much earlier), ect.
My main point is the claim of being keto-adapted being so much better than other avg diet is premised on false foundation that is not understood by advocates of it - many say you were burning carbs mainly or first all the time, many say you are burning more fat now at all times, or even suggesting the rate goes up.
I have no issues with the other claims - easier to eat less. Since this is personal - could very well be the case.5
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