Advanced calorie deficits (Fair Warning - long post)
Replies
-
Glucose and ketones are the brains preferred fuels, but fat is the preferred fuel of muscle especially in aerobic conditions. This is why your liver converts all excess carbs via into fatty acids for storage.
This is kinda true. I say that because when muscle is in a resting state, there's a balance between glycogen and FFA usage depending on serum glucose levels in the body, low serum levels means more glycogen usage. I can't speak to whether that's the reason why the body converts energy into FFA's, I've never read any studies postulating that before. To me it was just common sense, the body will use the most efficient storage path, with 9 calories per g for lipids vs 4 (+-) for carbohydrates, it's just reasonable to assume it will use the most efficient storage method. Whether that's accurate, I don't know. But if you have some studies or research that shows evidence of reasoning for conversion to lipids, I would truely like to read it.
I'm not being snarky at all, I mean it, I would like to read any information you have.
I make no bones about my own knowledge level, there's plenty I don't know, even after studying this stuff for many years. I'm always willing to learn more, and not afraid to say when I'm mistaken or misinformed about something.
Actually the whole explanation of fat metabolism was off as well. Triglycerides have a glycerol backbone. When the fats are being metabolized they are not converted to glucose. The fat is burned and then the glycerol backbone is released from the triglyceride and it is converted to glucose for storage as glycogen, release to the blood, or immediate consumption depending on the situation. You are correct that glucose is burned when blood serum glucose levels are high. However, I would consider this more of a disposal mechanism that a normal state of metabolism as your body does everything it can to quickly return blood glucose levels to normal after eating carbs. The preferred fuel for the body is fat and only during intense periods of exercise do your muscles rely on glycogen.0 -
Bumping for later.....this is interesting stuff for me. I just need to understand it better.0
-
Actually the whole explanation of fat metabolism was off as well. Triglycerides have a glycerol backbone. When the fats are being metabolized they are not converted to glucose. The fat is burned and then the glycerol backbone is released from the triglyceride and it is converted to glucose for storage as glycogen, release to the blood, or immediate consumption depending on the situation. You are correct that glucose is burned when blood serum glucose levels are high. However, I would consider this more of a disposal mechanism that a normal state of metabolism as your body does everything it can to quickly return blood glucose levels to normal after eating carbs. The preferred fuel for the body is fat and only during intense periods of exercise do your muscles rely on glycogen.
I think maybe there was some confusion in my explanation of fat metabolism. The confusion is probably 2 fold first from my trying to keep it as simple as possible and leaving out a step, basically I didn't talk about the conversion to triglycerides before I talk about the cleaving of glycerol and FFA's. And second not specifying that I was talking about adipose tissue only, not ingested triglycerides.
And also, upon rereading I should also kick myself for not explicitly stating (but rather implying) that I was talking about during a state of increased activity.0 -
Glucose and ketones are the brains preferred fuels, but fat is the preferred fuel of muscle especially in aerobic conditions. This is why your liver converts all excess carbs via into fatty acids for storage.
This is kinda true. I say that because when muscle is in a resting state, there's a balance between glycogen and FFA usage depending on serum glucose levels in the body, low serum levels means more glycogen usage. I can't speak to whether that's the reason why the body converts energy into FFA's, I've never read any studies postulating that before. To me it was just common sense, the body will use the most efficient storage path, with 9 calories per g for lipids vs 4 (+-) for carbohydrates, it's just reasonable to assume it will use the most efficient storage method. Whether that's accurate, I don't know. But if you have some studies or research that shows evidence of reasoning for conversion to lipids, I would truely like to read it.
I'm not being snarky at all, I mean it, I would like to read any information you have.
I make no bones about my own knowledge level, there's plenty I don't know, even after studying this stuff for many years. I'm always willing to learn more, and not afraid to say when I'm mistaken or misinformed about something.
Actually the whole explanation of fat metabolism was off as well. Triglycerides have a glycerol backbone. When the fats are being metabolized they are not converted to glucose. The fat is burned and then the glycerol backbone is released from the triglyceride and it is converted to glucose for storage as glycogen, release to the blood, or immediate consumption depending on the situation. You are correct that glucose is burned when blood serum glucose levels are high. However, I would consider this more of a disposal mechanism that a normal state of metabolism as your body does everything it can to quickly return blood glucose levels to normal after eating carbs. The preferred fuel for the body is fat and only during intense periods of exercise do your muscles rely on glycogen.
Two questions:
1. What do you mean when you say "fat is burned"?
2. When talking about preferred fuel, you mention glycogen, but from what I have read, glucose is the fuel we are talking about for preference (versus fat and ketones). Does the formula still hold for glucose vs. fat/ketones? Maybe my understanding about glucose --> glycogen or glycogen --> glucose is wrong.0 -
bump for another time0
-
Not to speak for him but I think he means the FFA's are burned directly in that particular statement.
Two questions:
1. What do you mean when you say "fat is burned"?
2. When talking about preferred fuel, you mention glycogen, but from what I have read, glucose is the fuel we are talking about for preference (versus fat and ketones). Does the formula still hold for glucose vs. fat/ketones? Maybe my understanding about glucose --> glycogen or glycogen --> glucose is wrong.
glycogen is essentially a chain of glucose molecules.0 -
Bump to read later.0
-
Interesting read. I will read through more of the comments later on. Reading this should help me out with my new WOL
0 -
Not to speak for him but I think he means the FFA's are burned directly in that particular statement.
Two questions:
1. What do you mean when you say "fat is burned"?
2. When talking about preferred fuel, you mention glycogen, but from what I have read, glucose is the fuel we are talking about for preference (versus fat and ketones). Does the formula still hold for glucose vs. fat/ketones? Maybe my understanding about glucose --> glycogen or glycogen --> glucose is wrong.
glycogen is essentially a chain of glucose molecules.
I see, thanks. But, as for glycogen/glucose, if there is an extra step in cleaving the glycogen (which I assume there is), does that mean the statement "fat/ketones is preferred over glycogen" is different than the statement "fat/ketones is preferred over glucose"?0 -
I see, thanks. But, as for glycogen/glucose, if there is an extra step in cleaving the glycogen (which I assume there is), does that mean the statement "fat/ketones is preferred over glycogen" is different than the statement "fat/ketones is preferred over glucose"?
the process is known as Glycogen phosphorylase and as far as I know there is minimal differentiation. But someone better than me at enzymatic breakdowns and cellular biochemistry may be required to answer that with more certainty.0 -
This site is great, perfect for a person to start trying to lose weight. But as we progress through the stages of weight loss, it becomes harder to estimate how many calories you need to reach metabolic homoeostasis and therefore to predict what you need to reach calorie deficit without going to far and entering into a state where the body will recognize a constant and high calorie deficit and compensate by lowering overall calorie consumption and ramping up fat storage (commonly known as starvation mode but more accurately known as adaptive thermogenesis or the famine response.......
A much better way is to eat the correct number of calories to keep your body "thinking" it's got plenty of energy, then use exercise to elicit that deficit we all want, which forces the body to pull small amounts of fat to make up the difference while still having plenty of "fast" energy (in the form of carbohydrates) to fuel the exercise itself. Things that require a slower trickle of energy like breathing, walking, doing the dishes, sweeping the floor...etc. (very low stress activities) can be supplemented by fat. In every study done that I've ever read (and that's hundreds), fat energy isn't tapped into by the moderate to high level activity until at a minimum the 15 minute mark, and most not seeing fat reserve usage until well after 30 minutes...
Conclusion:
All this being said, what's the point? Well the point is to get you, the informed human, thinking about more than just calories in vs. calories out. If you're struggling to lose weight. Do some really thoughtful analysis, figure out what area you're probably lacking in, tweak your routine or diet then give it TIME to let your body adjust. Then re-analyze and decide whether it's working, if not, keep tweaking. Use your knowledge. Don't become frustrated with the process, treat it like a challenge. Knowledge will eventually allow you to succeed.
Hope this is useful to someone. Feel free to comment, question, even debate.
Regards
-Steve H.
Hi, thank you for the informative post. I do have a question, but I will preface it by saying that I am not a scientist but am striving to be more informed. The question is this - to avoid the body adapting to prolonged calorie deficit wouldn't another method be to vary calorie consumption, I am thinking in terms of consuming at or around TDEE for the majority of the time and then having a couple of very low calorie days a week to achieve the necessary deficit (it's basically the 5:2 plan)?0 -
Hi, thank you for the informative post. I do have a question, but I will preface it by saying that I am not a scientist but am striving to be more informed. The question is this - to avoid the body adapting to prolonged calorie deficit wouldn't another method be to vary calorie consumption, I am thinking in terms of consuming at or around TDEE for the majority of the time and then having a couple of very low calorie days a week to achieve the necessary deficit (it's basically the 5:2 plan)?
I've done quite a bit of research into IF (Intermittent Fasting) and have even tried the method for about 2 months a couple of years ago. There are definitely some benefits to it, and yes, I feel it's a viable alternative. There are some drawbacks to it though, you must be very strict in your calorie consumption, which means very little variability in your totals, which also means very little variability in your workouts. It also requires a lot of will power as there are multiple days where you're eating next to nothing. The way our bodies work, it takes days for your body to register food depletion, and IF dances around this and takes advantage of the theory (which has been shown to be true in multiple studies) that for up to 3 days after beginning a fast, the body does NOT adjust to the calorie depletion and even slightly increases the overall metabolic rate assuming you don't prematurely deplete your energy reserves.
So yeah, IF is a possibility, but it's a much different topic than starvation mode as you are actually doing a mini-refeed every week.0 -
- Whether you want to believe it or not, starvation mode is real
Many people may have the wrong idea of what starvation mode is, but that doesn't make it false, it makes their concept of it false. It's up to us as intelligent human beings to combat misinformation where ever we can. That means when someone spouts something wrong or silly about starvation mode. Speak up. But do it respectfully, and provide not just a response, but proof. There's plenty out there I can give you tons of studies if you need them. But just talking about the metabolic processes surrounding this state should be enough( no studies needed, these are facts about the body, not up for debate). What starvation mode isn't: it has nothing to do with 1200 calories, it doesn't happen after 1 day of not eating, and it is NOT starvation (two completely separate terms), starvation is a state, starvation mode is a process. Yes someone in prolonged, deep starvation mode can eventually starve, but except in the case of complete absence of food, starvation istself is extremely rare and someone giving you case studies on starvation to prove points on starvation mode are only showing their scientific ignorance.
Starvation mode IS, in it's simplest form, your body's metabolic processes recognizing, over the course of days or more likely weeks, that it's receiving far fewer calories than it needs. This triggers two major functions. First, when in starvation mode the body will reduce energy consumption wherever it can, starting with the least important (in it's opinion) functions first. Second the body will use any extra calories it can find and store them as fat. So when someone says starvation mode is a myth, please try to explain that it's not a myth, it's just difficult to prove, and you can't just blithely say someone's in that state without some serious analysis.
Sources please? I'm interested in where you are getting this.
Here's what I found in the scientific, peer-reviewed literature:
http://www.ncbi.nlm.nih.gov/pubmed/23404923
Müller MJ, Bosy-Westphal A. Adaptive thermogenesis with weight loss in humans. Obesity (Silver Spring). 2013 Feb;21(2):218-28.
The authors say the data are still ambiguous to what extent adaptive thermogenesis (changes to the resting energy expenditure as a result of underfeeding) exists, when corrected for loss in fat-free mass and fat mass. Some studies see it, some don't, some see the opposite effect, and some are using different definitions.
http://www.ncbi.nlm.nih.gov/pubmed/19710198
(Same group as above) Contribution of individual organ mass loss to weight loss-associated decline in resting energy expenditure. Am J Clin Nutr. 2009 Oct;90(4):993-1001.
This one you can read for free. They put obese women on very low calorie diets (800-1000 Calories) for 12 weeks and measured changes in their body composition and resting energy expenditures. The amount of adaptive thermogenesis that was not explained by loss in organ/fat/muscle tissue was on average about 50 Calories per day. 50 Cal from the fairly extreme restriction here doesn't seem like a huge concern to me, certainly not worth all the hoopla that we give it.
Given, in these studies, and any study with human participants, the subjects are given diets carefully designed to be low in energy but nutritionally complete. Maybe what you are talking about has to do with people who are not getting enough of certain micronutrients? Protein?
http://www.ncbi.nlm.nih.gov/pubmed/1615886
Prentice AM, Jebb SA, Goldberg GR, Coward WA, Murgatroyd PR, Poppitt SD, Cole TJ. Effects of weight cycling on body composition. Am J Clin Nutr. 1992 Jul;56(1 Suppl):209S-216S.
If very low calorie diets cause rebound fat storage, you would expect that "yo-yo"-ing would cause a net increase in fat, decrease in lean body mass, right? That's not what these authors found in a population of people in a time and place in the world that had annual "hungry seasons." Their body composition as they aged was the same as people who did not have periodic extreme calorie restriction.
http://www.ncbi.nlm.nih.gov/pubmed/21677272
Maclean PS, Bergouignan A, Cornier MA, Jackman MR. Biology's response to dieting: the impetus for weight regain. Am J Physiol Regul Integr Comp Physiol. 2011 Sep;301(3):R581-600.
Also a review that is freely available. Looks like the biochemical signals from the newly-shrunk fat cells are because they used to be bigger. As in, it isn't because of recent calorie restriction directly (what you call "starvation mode"), but because of the fat loss itself (regardless of how it was lost).
Seems to me, if wanted to test if cessation of a very low calorie diet caused preferential fat deposition, one way to do it would be to compare two groups of people- one who ended up in "starvation mode" from severe caloric restriction, and one who lost the same amount of weight otherwise (slower, more exercise, etc), matched for activity level and diet. Then after a period of time, measure their body composition.
I haven't seen an experiment like this- what I did find was:
http://www.ncbi.nlm.nih.gov/pubmed/11010936
Weyer C, Walford RL, Harper IT, Milner M, MacCallum T, Tataranni PA, Ravussin E. Energy metabolism after 2 y of energy restriction: the biosphere 2 experiment. Am J Clin Nutr. 2000 Oct;72(4):946-53.
People were on a ~1800 Calorie diet for 2 years. Which doesn't qualify as "starvation mode," at least according to MFP. They lost ~15% of their body mass. Six months afterward, free to make all their own food choices, they gained the weight back, but it was almost all fat.
So, yeah, it looks like any kind of rapid weight gain results in preferential fat gains, particularly if there used to be more fat tissue at some point. Fat is just easier and quicker to grow than muscle.
So... I'm curious. What are you reading? I came across a few other studies, but none comparing animals or people that lost weight gradually with those that lost weight with extreme calorie restriction, and thus cannot differentiate between effects of fat loss and effects of low calorie intake. Have you seen something with this control?
I'm obviously not a big believer in "starvation mode." Yeah, losing fat and cutting calories makes many changes in your body, but to call it a discrete "mode," that triggers the two things you said... I'm not seeing it in the literature, at least in what I perused this evening in pubmed.
Thanks!0 -
Bump0
-
bump0
-
Sources please? I'm interested in where you are getting this.
And a means of keeping it at bay. For those skimming rather than digging - they did little to no exercise prior to this study and added exercise - it was resistance for them.
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004377
Participants had to be between BMI 25-30, overweight category, but healthy otherwise. They were excluded if they smoked, exercised more than twice a week, were pregnant, lactating or post-menopausal, had a history of obesity (BMI>32), diabetes, cardiovascular disease, eating disorders, psychological disorders, substance abuse or regularly used medications except for birth control. So that may have a bearing in comparison.
Diet was 55 / 15 / 30 for C / P / F.
CR (Calorie Restriction) was 25% deficit from TDEE, so not massive.
CR + EX (EXercise) was 12.5% deficit plus 12.5% calories burned in cardio exercise 5 x week, each session being 403-569 calories for 45-53 min (women and men difference).
LCD (Low Calorie Diet) was 890 cal/day until 15% of weight was loss, then back to maintenance calories by month 3, whatever it was then. That's a tad massive
DEXA scans for body composition of LBM (Fat Free Mass (FFM)) and Fat Mass (FM).
Sedentary TDEE measurements in a metabolic chamber for 23 hrs.
SMR (Sleeping Metabolic Rate (BMR)) measured chunk of night no movement in ventilation hood.
Several formulas related to measured Sedentary TDEE at baseline based on all available stats, to compare down the road when stats changed.
At 3 month check, sedentary TDEE had dropped by the following amounts, below what the formulas would have indicated for new measured LBM and FM, and SMR. In other words, it lowered the expected amount, and an additional...
CR - 371
CREX - 2
LCD - 496
At 6 month check, there was some recovery to be had, and reminder the LCD was at maintenance this entire time from 3-6 months...
CR - 209
CREX - 129 over expected
LCD - 275
So notice that even after 3 months maintenance level eating, the initial LCD group still had a TDEE 275 below what was expected for their current LBM and FM. Perhaps more time at maintenance it would have recovered?
The CR group slightly recovered, but still 209 lower than expected.
The CR+EX group actually had an increased TDEE.
Now that was Sedentary TDEE in the lab that was compared.
Daily TDEE with all activity was also compared to their SMR, TDEE/SMR for physical activity rate (PAR).
At month 3, CR and LCD had significant drops in PAR below what would have been expected for their current LBM and FM, by CR 350 and LCD 497, with CR-EX having none. At month 6, CR 215 and LCD 241, so again some recovery.
So the NEAT part of their day decreased as expected because of lower weight, but even more than expected because of less movement compared to pre-diet, resulting in lowered figures above.
Study also indicates an efficiency change not clarified by those measured changes.0 -
bump0
-
in response to a request for sources please keep in mind this post is an anthology of topics so for this part I'll just list sources that touch on the starvation mode concept because that's what many people are focusing on. Please note that it wasn't the point of my post, my post was to get people thinking about fat loss differently, not to focus on starvation mode.
anyway, here are some that I had stashed away in the past. I haven't had time to go back and dig up all my research. Nor do I have time right now to give summaries of all of these, you'll just have to read the abstracts. these are all free so...
http://journals.cambridge.org/action/displayFulltext?type=1&fid=789564&jid=PNS&volumeId=54&issueId=01&aid=789556
http://www.ajcn.org/content/46/4/622.full.pdf+html
http://www.ajcn.org/content/68/1/1.full.pdf+html?sid=1f835bd6-51e1-49c0-a79e-e73fa166c490
http://www.ajcn.org/content/71/6/1511.full.pdf+html?sid=1f835bd6-51e1-49c0-a79e-e73fa166c490
http://www.ajcn.org/content/83/2/461S.full.pdf+html?sid=25df97eb-0ad2-4dbd-91a7-07d1ff371d19
http://jcem.endojournals.org/content/96/1/66.full?sid=fbb2018e-851b-468e-82d3-e0326c632ce4
http://www.ajcn.org/content/68/3/599.full.pdf+html?sid=0a679b54-6b93-4a1c-8ce1-88b3f0402baf0 -
further reading on what happens to fat in the human body under various conditions and in various states
http://www.ajcn.org/content/61/3/486.full.pdf+html?sid=13ed3002-6c8d-4b9b-9c50-eaea1d5b38a8
http://www.ajcn.org/content/73/3/523.full.pdf+html?sid=0a679b54-6b93-4a1c-8ce1-88b3f0402baf
http://www.ajcn.org/content/55/3/670.full.pdf+html?sid=0a679b54-6b93-4a1c-8ce1-88b3f0402baf
http://www.ajcn.org/content/72/2/558s.full.pdf+html?sid=35d57613-d25d-4127-ac75-0aa506b9db26
http://www.ajcn.org/content/61/4/968S.full.pdf+html?sid=35d57613-d25d-4127-ac75-0aa506b9db26
http://www.ajcn.org/content/57/5/752S.full.pdf+html?sid=35d57613-d25d-4127-ac75-0aa506b9db260 -
Bump for later0
-
Tagging post.
Would be really nice to see this in a sticky somewhere... Or may be added to the "links on MFP you want to reread"? For geeky noobs like me, that's the kind of info I am looking for.0 -
Bump0
-
Glucose and ketones are the brains preferred fuels, but fat is the preferred fuel of muscle especially in aerobic conditions. This is why your liver converts all excess carbs via into fatty acids for storage.
This is kinda true. I say that because when muscle is in a resting state, there's a balance between glycogen and FFA usage depending on serum glucose levels in the body, low serum levels means more glycogen usage. I can't speak to whether that's the reason why the body converts energy into FFA's, I've never read any studies postulating that before. To me it was just common sense, the body will use the most efficient storage path, with 9 calories per g for lipids vs 4 (+-) for carbohydrates, it's just reasonable to assume it will use the most efficient storage method. Whether that's accurate, I don't know. But if you have some studies or research that shows evidence of reasoning for conversion to lipids, I would truely like to read it.
I'm not being snarky at all, I mean it, I would like to read any information you have.
I make no bones about my own knowledge level, there's plenty I don't know, even after studying this stuff for many years. I'm always willing to learn more, and not afraid to say when I'm mistaken or misinformed about something.
Actually the whole explanation of fat metabolism was off as well. Triglycerides have a glycerol backbone. When the fats are being metabolized they are not converted to glucose. The fat is burned and then the glycerol backbone is released from the triglyceride and it is converted to glucose for storage as glycogen, release to the blood, or immediate consumption depending on the situation. You are correct that glucose is burned when blood serum glucose levels are high. However, I would consider this more of a disposal mechanism that a normal state of metabolism as your body does everything it can to quickly return blood glucose levels to normal after eating carbs. The preferred fuel for the body is fat and only during intense periods of exercise do your muscles rely on glycogen.
Two questions:
1. What do you mean when you say "fat is burned"?
2. When talking about preferred fuel, you mention glycogen, but from what I have read, glucose is the fuel we are talking about for preference (versus fat and ketones). Does the formula still hold for glucose vs. fat/ketones? Maybe my understanding about glucose --> glycogen or glycogen --> glucose is wrong.
When I say fat is "burned" I really mean metabolized.
I used glucose and glycogen interchangeably. However, during periods of intense exercise my understanding states that muscles will draw down stored glycogen stores and pull from blood glucose for energy. Your liver will try to maintain blood glucose levels and also generate ketones depending on liver stores of glycogen (which are relatively small). Glycogen is released in your muscles as glucose when needed. You muscles in aerobic conditions will tend to metabolize fat over glucose and this is greatly affected by dietary choices. However, fat metabolization is preferable for many reasons.0 -
Bump for later0
-
Thanks- I plan to read these and comment when I have more time this weekend. It takes some time to look at exactly what they are saying, what they did, what controls were done, etc, and what it has to do with the concept of a "starvation mode."
First glance- from the article in heybales's post- the numbers posted regarding a drop in energy expended beyond that expected are TDEE, not basal metabolic rate, which I think is what people generally mean when they talk about a drop in "metabolism." Looks like they are saying people who were on low calorie diets (without exercise) ended up with the "behavioral adaptation" of moving less throughout the day. In fig 4, they show the drop in metabolic rate (measured during sleep) in Cal/day before and after caloric restriction was a more modest ~130 Calories/day, and this number does not account for changes in weight and body composition. Also the group on a lower calorie diet lost more weight total (fig 2). But... I didn't read the whole thing yet, just looked at the figures. Thanks for posting.
Any researchers in this field care to chime in?0 -
Thank you for sharing your knowledge. The article content is thought provoking and a boost to help me on my health journey.0
-
Thanks- I plan to read these and comment when I have more time this weekend. It takes some time to look at exactly what they are saying, what they did, what controls were done, etc, and what it has to do with the concept of a "starvation mode."
First glance- from the article in heybales's post- the numbers posted regarding a drop in energy expended beyond that expected are TDEE, not basal metabolic rate, which I think is what people generally mean when they talk about a drop in "metabolism." Looks like they are saying people who were on low calorie diets (without exercise) ended up with the "behavioral adaptation" of moving less throughout the day. In fig 4, they show the drop in metabolic rate (measured during sleep) in Cal/day before and after caloric restriction was a more modest ~130 Calories/day, and this number does not account for changes in weight and body composition. Also the group on a lower calorie diet lost more weight total (fig 2). But... I didn't read the whole thing yet, just looked at the figures. Thanks for posting.
Any researchers in this field care to chime in?
In many of the studies that I posted, you will see that there is a drop in the RMR after about 72 hours (after an initial minor increase in energy which is postulated to be because of the energy needed to convert fat stores), which continues throughout the starvation period and underfeeding periods (depending on which study you are looking at). Most talk about the depletion of glycogen reserves and the transition to a lower level of insulin production0 -
Thanks- I plan to read these and comment when I have more time this weekend. It takes some time to look at exactly what they are saying, what they did, what controls were done, etc, and what it has to do with the concept of a "starvation mode."
First glance- from the article in heybales's post- the numbers posted regarding a drop in energy expended beyond that expected are TDEE, not basal metabolic rate, which I think is what people generally mean when they talk about a drop in "metabolism." Looks like they are saying people who were on low calorie diets (without exercise) ended up with the "behavioral adaptation" of moving less throughout the day. In fig 4, they show the drop in metabolic rate (measured during sleep) in Cal/day before and after caloric restriction was a more modest ~130 Calories/day, and this number does not account for changes in weight and body composition. Also the group on a lower calorie diet lost more weight total (fig 2). But... I didn't read the whole thing yet, just looked at the figures. Thanks for posting.
Any researchers in this field care to chime in?
That's not how I'm interpreting it. If you read the discussion, they clearly (in the second paragraph) state that they observed a real metabolic adaptation even after TDEE was adjusted for the lower metabolic rates of reduced FFM and FM.
here's the quote from the part I am talking about:
"Now for the first time, we objectively characterized the response in all the components of daily energy expenditure to caloric restriction by combining doubly labeled water and indirect calorimetry (Figure 4). In response to caloric restriction (CR/LCD) we observed a true metabolic adaptation at months 3 and 6 of the intervention. To exclude the contribution of sedentary energy expenditure (the largest component of daily energy expenditure), we adjusted TDEE for sedentary energy expenditure (24h-EE and SMR) and observed that measured TDEE was significantly less than predicted at both month 3 and month 6 of CR. Interestingly no metabolic adaptation was observed in CR+EX. Together, this data indicates that TDEE is reduced with caloric restriction and is likely the result of a metabolic adaptation in the sedentary state accompanied by a reduction in activity-related energy expenditure and reduced levels of physical activity (Figure 3). Therefore, this study supports a ‘metabolic adaptation’ in response to weight loss in humans and demonstrates for the first time a reduction in all components of daily energy expenditure with dietary-induced weight loss, including the level physical activity. Importantly, CR in combination with exercise (CR+EX) did not result in metabolic adaptation while inducing similar changes in body composition as with CR alone."
for the record, even though this is a much longer term study then the ones I posted, most of the data correlates with some minor variation. I especcially love the study done by MacDonald and Webber called Feeding, fasting and starvation: factors affecting fuel utilization. I believe it's the first link I posted, it's the one that goes to cambridge.org0 -
You wrote "The less fat you have the more difficult it is to keep a deficit"
I'm not sure what you are trying to say there. First off, the three energy systems are in constant use, lipid oxidation is a permanent process, it's use, in terms of energy availability varies but it is still always present. Fat is constant being liberated and free plasma fatty acids are sufficient for exercise needs in excess of hours in the non- fasting individual. While fat does have a metabolic cost, to release it's incorrect to think of it in terms of an energy cost but rather a enzymatic/conversion rate cost. You can only deliver so much free FA at any time.
If anything, the less LBM you have, the more difficult it is to keep a deficit.0 -
Glucose and ketones are the brains preferred fuels, but fat is the preferred fuel of muscle especially in aerobic conditions. This is why your liver converts all excess carbs via into fatty acids for storage.
This is kinda true. I say that because when muscle is in a resting state, there's a balance between glycogen and FFA usage depending on serum glucose levels in the body, low serum levels means more glycogen usage. I can't speak to whether that's the reason why the body converts energy into FFA's, I've never read any studies postulating that before. To me it was just common sense, the body will use the most efficient storage path, with 9 calories per g for lipids vs 4 (+-) for carbohydrates, it's just reasonable to assume it will use the most efficient storage method. Whether that's accurate, I don't know. But if you have some studies or research that shows evidence of reasoning for conversion to lipids, I would truely like to read it.
I'm not being snarky at all, I mean it, I would like to read any information you have.
I make no bones about my own knowledge level, there's plenty I don't know, even after studying this stuff for many years. I'm always willing to learn more, and not afraid to say when I'm mistaken or misinformed about something.
Actually the whole explanation of fat metabolism was off as well. Triglycerides have a glycerol backbone. When the fats are being metabolized they are not converted to glucose. The fat is burned and then the glycerol backbone is released from the triglyceride and it is converted to glucose for storage as glycogen, release to the blood, or immediate consumption depending on the situation. You are correct that glucose is burned when blood serum glucose levels are high. However, I would consider this more of a disposal mechanism that a normal state of metabolism as your body does everything it can to quickly return blood glucose levels to normal after eating carbs. The preferred fuel for the body is fat and only during intense periods of exercise do your muscles rely on glycogen.
Two questions:
1. What do you mean when you say "fat is burned"?
2. When talking about preferred fuel, you mention glycogen, but from what I have read, glucose is the fuel we are talking about for preference (versus fat and ketones). Does the formula still hold for glucose vs. fat/ketones? Maybe my understanding about glucose --> glycogen or glycogen --> glucose is wrong.
When I say fat is "burned" I really mean metabolized.
I used glucose and glycogen interchangeably. However, during periods of intense exercise my understanding states that muscles will draw down stored glycogen stores and pull from blood glucose for energy. Your liver will try to maintain blood glucose levels and also generate ketones depending on liver stores of glycogen (which are relatively small). Glycogen is released in your muscles as glucose when needed. You muscles in aerobic conditions will tend to metabolize fat over glucose and this is greatly affected by dietary choices. However, fat metabolization is preferable for many reasons.
Liver stores of glycogen are not small. It about 10-15 percent of total organ weight and really, along with plasma stores, the primary source for non-muscle organs.0
Categories
- All Categories
- 1.4M Health, Wellness and Goals
- 393.6K Introduce Yourself
- 43.8K Getting Started
- 260.3K Health and Weight Loss
- 175.9K Food and Nutrition
- 47.5K Recipes
- 232.5K Fitness and Exercise
- 431 Sleep, Mindfulness and Overall Wellness
- 6.5K Goal: Maintaining Weight
- 8.6K Goal: Gaining Weight and Body Building
- 153K Motivation and Support
- 8K Challenges
- 1.3K Debate Club
- 96.3K Chit-Chat
- 2.5K Fun and Games
- 3.8K MyFitnessPal Information
- 24 News and Announcements
- 1.1K Feature Suggestions and Ideas
- 2.6K MyFitnessPal Tech Support Questions