Eating Below your BMR... Why is it bad?

Aineko

???
actually, just a quick search on ncbi returned some "non-existent" studies. for example:
http://www.ncbi.nlm.nih.gov/pubmed/18842775

pay attention to "total energy expenditure -- in particular, energy expenditure at low levels of physical activity -- is lower than predicted by actual changes in body weight and composition."

and if you go through reference list of this paper you'll find more.

I don't understand how people throw around statements like "there are no studies supporting..." without checking themselves if this was really true...

For some reason, I can't read the whole article, but the abstract seemed like it was more about how after weight loss, there is a slower metabolism that doesn't "bounce back" right away. I've seen other studies that do suggest that it does.

But I didn't see anything in the abstract about eating above/below your BMR.

I don't doubt there are studies showing different results (as I mentioned this was a very quick search), but without reading them in details and paying attention to all the factors monitored in different studies, we can hardly come to any conclusion. Unfortunately, I am not aware of any meta-analysis done on this subject, that would be a good one to look at.
My post was a direct response to a post claiming "there are no studies showing that dieting affects your metabolism and all the metabolism changes are due to reduction of body mass".

no, you won't find anything about under/over BMR dieting - I wasn't searching for that . My understanding is that it isn't about any magic number (BMR, TDEE - 20% etc.), but rather about very high caloric def. over a prolonged period of time. how "high" and how "prolonged" will greatly depend on factors such as your initial weight/body fat, your genetics and similar. the hype about BMR might be coming from the fact that it accounts for about 70% of our daily energy needs, so in order to stay away from very high cal. def. ppl will tell you "if you don't want to eat anything else, at least eat your BMR". but as I said, I think it's more about how big your def. is. and of course, it is all about cost and benefits - if someone is obese and benefits of losing weight as quickly as possible are greater than the risks of a potential metabolic response, then sure, go for it! but be smart and when you hit the plateau don't go with your first instinct to eat even less. (and please, no conc camp references, that's nonsense - those ppl weren't given a chance to develop any kind of adaptive metabolic response to low calorie intake, they were simply starved to death. the lucky ones lived long enough to be released).

wiscyproblems

Sounds bogus to me, I believe its just made up and spread over and over on the MFP forums.

Why would your body attack muscle first instead of fat for energy? That would be quite stupid

I can see it using muscle for protein it needs, but not energy.

I don't believe your BMR is the magical cut off for your body to start eating your muscle tissue, if someone can prove to me otherwise I stand corrected

Glucose is energy. When the body runs low on carbs/glucose then it may use amino acids in a process to make energy. No there is no magical cut off number, but what if you are consecutively not giving your body the glucose that it needs and it has to continuously break down the muscle for energy?
http://www.livestrong.com/article/554481-when-does-the-body-start-to-use-muscle-tissue-for-energy/
http://science.howstuffworks.com/environmental/life/human-biology/fat-cell.htm

This is not true. Your body will metabolize substances/nutrients in this order: alcohol, glucose/carbs, fat, muscle.

Masterdo

Sounds bogus to me, I believe its just made up and spread over and over on the MFP forums.

Why would your body attack muscle first instead of fat for energy? That would be quite stupid

I can see it using muscle for protein it needs, but not energy.

I don't believe your BMR is the magical cut off for your body to start eating your muscle tissue, if someone can prove to me otherwise I stand corrected

Glucose is energy. When the body runs low on carbs/glucose then it may use amino acids in a process to make energy. No there is no magical cut off number, but what if you are consecutively not giving your body the glucose that it needs and it has to continuously break down the muscle for energy?
http://www.livestrong.com/article/554481-when-does-the-body-start-to-use-muscle-tissue-for-energy/
http://science.howstuffworks.com/environmental/life/human-biology/fat-cell.htm

This is not true. Your body will metabolize substances/nutrients in this order: alcohol, glucose/carbs, fat, muscle.

This is from basic biology, where we learn how our body actually digests that stuff. Alcohol and Carbs digestion begins in the mouth with saliva, fat is processed in the stomach and proteins are digested mostly by the small intestine. That's the order you are referring too.

As far as catabolism (getting nutrients from fat stores/muscles/lean mass), I am really not aware of any science taking it down to an order like that, heck, we've seen here that they even struggle about the ratios at the moment, let alone the order...

DanielleRN8

BMR is what your body needs to simply survive. That is what would be burned if you just stayed in bed and did nothing. Your body NEEDS those calories to work correctly and keep the systems going. When your body can not get the calories it needs, then it looks for them wherever it can get them. That could be fat, but it also will be muscle and other systems. The thing is, it will not be just fat!

Your TDEE is where you take your deficit from. This is how much you burn based off of your daily activity.

Pretty much what I was going to say. You have to eat at least your bmr to keep you from burning your muscle for energy.

kenny_johnson

Well, the muscle breakdown is just basic physiology, but that doesn't appear to be the points under your request.

Here are the studies showing just how well ones can slow down and stall weight loss, because of eating to low.

Also check out almost any site on diet and weight loss and they'll share the fact your metabolism will slow down. Usually it's stated as if it must happen. But it doesn't have to unless you think you are going to get big losses the whole time.

http://www.ncbi.nlm.nih.gov/pubmed/11430776

http://www.ncbi.nlm.nih.gov/pubmed/19660148

http://www.ncbi.nlm.nih.gov/pubmed/20054213

http://www.ncbi.nlm.nih.gov/pubmed/17260010

Oh, and 1 kilojoule is 238.8 calories as we would normally call it.

Thanks for actually providing cited sources.Although to be honest, most of them are over my head. Too much technical speak for my little brain. With that said, I still don't see an answer to my original question. Why is eating at or above BMR "OK" but eating below BMR "bad."

treetop57

http://www.ncbi.nlm.nih.gov/pubmed/11430776

Evidence for the existence of adaptive thermogenesis during weight loss.
Doucet E, St-Pierre S, Alméras N, Després JP, Bouchard C, Tremblay A.
Source

Division of Kinesiology, Laval University, Ste-Foy, Québec G1K 7P4, Canada.
Abstract

The present study was performed to further investigate the adaptive component of thermogenesis that appears during prolonged energy restriction. Fifteen obese men and twenty obese women underwent a 15-week weight-loss programme. During this programme, body weight and composition as well as resting energy expenditure (REE) were measured at baseline, after 2 and 8 weeks of energy restriction (-2929 kJ/d [-700 kcal]) and drug therapy (or placebo), and finally 2-4 weeks after the end of the 15-week drug therapy and energy restriction intervention, when subjects were weight stable. Regression equations were established in a control population of the same age. These equations were then used to predict REE in obese men and women at baseline, after 2 and 8 weeks, as well as after the completion of the programme. In both men and women body weight and fat mass were significantly reduced in all cases) while fat-free mass remained unchanged throughout the programme. At baseline, REE predicted from the regression equation was not significantly different from the measured REE in men, while in women the measured REE was 13 % greater than predicted. After 2 weeks of energy restriction, measured REE had fallen by 469 and 635 kJ/d [112 and 151 kcal/day] and more than predicted and this difference reached 963 and 614 kJ/d [230 and 147 kcal/day] by week 8 of treatment in men and women respectively. Once body-weight stability was recovered at the end of the programme, changes in REE remained below predicted changes in men (-622 kJ/d [-149 kcal/day]). However, in women changes in predicted and measured REE were no longer different at this time, even if the women were maintaining a reduced body weight. In summary, the present results confirm the existence of adaptive thermogenesis and give objective measurements of this component during weight loss in obese men and women, while they also emphasize that in women this component seems to be essentially explained by the energy restriction.

I'm not sure exactly what the difference is between REE and BMR. The abstract mentions drug therapy and placebo, but gives no indication of what drug or whether the drug showed any difference from the placebo.

Apparently, the study found that the resting metabolism of men slowed by about 230 kcals/day after 8 weeks on a diet with a 700 kcal deficit. No indication whether 700 kcal deficit put them above or below BMR. The resting metabolism of women slowed by about 150 kcals/day, again with the 700 kcal deficit.

Apparently, the metabolism of men remained low by about 150 kcals/day after 2 to 4 weeks at maintenance, while the metabolism of the women returned to that predicted by their new weight.

In terms of muscle loss, this seems to be the key sentence: "In both men and women body weight and fat mass were significantly reduced in all cases while fat-free mass remained unchanged throughout the programme." So a 700 kcal deficit for 8 weeks resulted in little muscle loss.

It would be interesting to know how well the weight loss conformed with the predicted 1 lb every 5 days implied by the 700 kcal deficit. I also wonder whether the diet was constant based on a 700 kcal deficit from initial REE or whether it was adjusted down as REE went down.

If I take the study at face value, it seems to mean that for an obese man at 8 weeks, slowing of the metabolism due to calorie restriction would make weight loss 1/2 pound per week less than predicted And for an obese woman, it would be about 1/4 pound per week less than predicted. (Assuming it really is true that 500 deficit results in 1 lb per week.)

ironanimal

Thanks for actually providing cited sources.Although to be honest, most of them are over my head. Too much technical speak for my little brain. With that said, I still don't see an answer to my original question. Why is eating at or above BMR "OK" but eating below BMR "bad."

Because gradually over time, constant eating below your BMR will lower your BMR and you get into a vicious cycle of having to eat less and less. Eating at or above your BMR is better because it ensures your body has enough energy and nutrition to sustain it's lean mass, and thus, a higher BMR.

drapes73

Ok.. Then why is a calorie deficit above BMR different than one below it? Wouldn't both eat muscle first?

Not sure you understand the difference between BRM and TDEE?

BMR = The calories your body needs to survive (in a healthy way) just lying down doing NOTHING. Breathing and being still. Not getting up to go the the bathroom. Not chewing gum. Not lifting up the remote control and changing channels.

TDEE = BMR AND all the activity you do all day long, be it exercise, walking to your car, having sex, whatever...

If you eat below BMR, you're not giving your body the MINIMUM it needs on a day-to-day basis, just to exist. You take the deficit from the TDEE because you will still be eating more than enough to survive but less than what you expend overall doing whatever it is you do during the day.

If your BMR is 1500 and your TDEE is 2000 that means you have burned an additional 500 calories through activity. Whether you eat 1350 calories or 1750 calories your body is still at a deficit for the day. By your logic eating 1750 calories won't give your body MINIMUM it needs since your net is below your BMR. A calorie burned to keep your heart beating and a calorie burned climbing a stair are the same. Your body doesn't magically burn fat when you walk but burn muscle when your heart beats if you aren't feeding it enough.

heybales

http://www.ncbi.nlm.nih.gov/pubmed/11430776

Evidence for the existence of adaptive thermogenesis during weight loss.
Doucet E, St-Pierre S, Alméras N, Després JP, Bouchard C, Tremblay A.
Source

Division of Kinesiology, Laval University, Ste-Foy, Québec G1K 7P4, Canada.
Abstract

The present study was performed to further investigate the adaptive component of thermogenesis that appears during prolonged energy restriction. Fifteen obese men and twenty obese women underwent a 15-week weight-loss programme. During this programme, body weight and composition as well as resting energy expenditure (REE) were measured at baseline, after 2 and 8 weeks of energy restriction (-2929 kJ/d [-700 kcal]) and drug therapy (or placebo), and finally 2-4 weeks after the end of the 15-week drug therapy and energy restriction intervention, when subjects were weight stable. Regression equations were established in a control population of the same age. These equations were then used to predict REE in obese men and women at baseline, after 2 and 8 weeks, as well as after the completion of the programme. In both men and women body weight and fat mass were significantly reduced in all cases) while fat-free mass remained unchanged throughout the programme. At baseline, REE predicted from the regression equation was not significantly different from the measured REE in men, while in women the measured REE was 13 % greater than predicted. After 2 weeks of energy restriction, measured REE had fallen by 469 and 635 kJ/d [112 and 151 kcal/day] and more than predicted and this difference reached 963 and 614 kJ/d [230 and 147 kcal/day] by week 8 of treatment in men and women respectively. Once body-weight stability was recovered at the end of the programme, changes in REE remained below predicted changes in men (-622 kJ/d [-149 kcal/day]). However, in women changes in predicted and measured REE were no longer different at this time, even if the women were maintaining a reduced body weight. In summary, the present results confirm the existence of adaptive thermogenesis and give objective measurements of this component during weight loss in obese men and women, while they also emphasize that in women this component seems to be essentially explained by the energy restriction.

I'm not sure exactly what the difference is between REE and BMR. The abstract mentions drug therapy and placebo, but gives no indication of what drug or whether the drug showed any difference from the placebo.

Apparently, the study found that the resting metabolism of men slowed by about 230 kcals/day after 8 weeks on a diet with a 700 kcal deficit. No indication whether 700 kcal deficit put them above or below BMR. The resting metabolism of women slowed by about 150 kcals/day, again with the 700 kcal deficit.

Apparently, the metabolism of men remained low by about 150 kcals/day after 2 to 4 weeks at maintenance, while the metabolism of the women returned to that predicted by their new weight.

In terms of muscle loss, this seems to be the key sentence: "In both men and women body weight and fat mass were significantly reduced in all cases while fat-free mass remained unchanged throughout the programme." So a 700 kcal deficit for 8 weeks resulted in little muscle loss.

It would be interesting to know how well the weight loss conformed with the predicted 1 lb every 5 days implied by the 700 kcal deficit. I also wonder whether the diet was constant based on a 700 kcal deficit from initial REE or whether it was adjusted down as REE went down.

If I take the study at face value, it seems to mean that for an obese man at 8 weeks, slowing of the metabolism due to calorie restriction would make weight loss 1/2 pound per week less than predicted And for an obese woman, it would be about 1/4 pound per week less than predicted. (Assuming it really is true that 500 deficit results in 1 lb per week.)

Ya, sometimes the other details would be very interesting to know.

I'm merely guessing as you had indicated earlier, to find 700 cal to deficit, it would have to be from more than just daily activity, unless the BMR was approaching 4000, which is very doubtful even for obese men.

It is interesting how women would recover to whatever knew weight they were at, men would take longer than I guess the time of the study.

And what result to the study since the metabolism slowed down this much already. And what if exercise had been included, or was it? Usually on here, it's when someone adds exercise they find the loss stops after a bit.

The other study with just obese men stalling their loss too.

Glad you pointed out the lack of muscle loss. I'm really not sure where that got started that muscle loss would automatically happen.
In my mind, what extra muscle besides what is used for daily activity would there be to lose anyway, in someone that just started to diet? So that is used muscle in that case, like exercised muscle.

heybales

Not sure you understand the difference between BRM and TDEE?

BMR = The calories your body needs to survive (in a healthy way) just lying down doing NOTHING. Breathing and being still. Not getting up to go the the bathroom. Not chewing gum. Not lifting up the remote control and changing channels.

TDEE = BMR AND all the activity you do all day long, be it exercise, walking to your car, having sex, whatever...

If you eat below BMR, you're not giving your body the MINIMUM it needs on a day-to-day basis, just to exist. You take the deficit from the TDEE because you will still be eating more than enough to survive but less than what you expend overall doing whatever it is you do during the day.

If your BMR is 1500 and your TDEE is 2000 that means you have burned an additional 500 calories through activity. Whether you eat 1350 calories or 1750 calories your body is still at a deficit for the day. By your logic eating 1750 calories won't give your body MINIMUM it needs since your net is below your BMR. A calorie burned to keep your heart beating and a calorie burned climbing a stair are the same. Your body doesn't magically burn fat when you walk but burn muscle when your heart beats if you aren't feeding it enough.

Got that backwards actually. 1750 would give you body the calories it is willing to use for BMR functions, it wants 1500.

Masterdo

Thanks for actually providing cited sources.Although to be honest, most of them are over my head. Too much technical speak for my little brain. With that said, I still don't see an answer to my original question. Why is eating at or above BMR "OK" but eating below BMR "bad."

Because gradually over time, constant eating below your BMR will lower your BMR and you get into a vicious cycle of having to eat less and less. Eating at or above your BMR is better because it ensures your body has enough energy and nutrition to sustain it's lean mass, and thus, a higher BMR.

Exactly! The BMR is not just a number, it is the best calorie burner you have available (except if you burn 1500-2000 cals a day, then you can safely ignore this...). Lowering that burn should be the last thing you want to do.


The studies cited that show effects on Resting Energy Expenditure (REE), Non Resting Energy Expenditure (NREE, this is what you burn when you actually workout. And it goes down when it has to) and incidentally, Total Energy Expenditure (TEE) are the worst possible news to someone trying to lose weight. It says that you can basically take the motor that burns the most calories in your day, and slow it down.

nz_deevaa

I lose the same amount each week eating at my BMR (1750 + exercise cals) as I did eating 1200 + exercise cals.

Plus my hair has stopped falling out.

I don't care WHY it's bad to eat below BMR, I just know it wasn't doing ME any extra benefit.

Aineko

Ok.. Then why is a calorie deficit above BMR different than one below it? Wouldn't both eat muscle first?

I see you keep repeating this question, which is fair enough . the answer is: because your body's response to calorie deficit is different/changes with time depending on the signals you are giving it. It is not a simple "input equals output" mechanism, but rather think of it as of a computer chip programmed to analyse various inputs and produce adequate 'commands'. The signal your body perceives on a low caloric deficit or zig-zag diets is completely different from the signal it gets from being on a high deficit over a long time. in one case the 'command' is "ok, burn a little bit of that fat, that;s what reserves are for", in the other case the 'command' becomes "*kitten*! there is no enough food out there to sustain even our basic needs! we must be in a middle of famine and we've no idea how long it's gonna go for. focus on preserving our energy reserve - slow down basic metabolism, reduce muscles (metabolically demanding tissue)!". (this is oversimplified of course, but you get the idea. and please note that I am not saying that you won't lose weight if you are overweight and go on a high deficit diet - you will, but we are talking about the unwanted consequences of losing your lean mass too and loss of a lean mas in these diets has been documented in studies already cited in this thread).

Helloitsdan

Skinny fat!

Aineko

Here's an interesting read (re different signals we are sending to our bodies):

Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss?
Varady KA.
Source
Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, IL 60612, USA. varady@uic.edu
Abstract
Dietary restriction is an effective strategy for weight loss in obese individuals. The most common form of dietary restriction implemented is daily calorie restriction (CR), which involves reducing energy by 15-60% of usual caloric intake every day. Another form of dietary restriction employed is intermittent CR, which involves 24 h of ad libitum food consumption alternated with 24 h of complete or partial food restriction. Although both diets are effective for weight loss, it remains unknown whether one of these interventions produces superior changes in body weight and body composition when compared to the other. Accordingly, this review examines the effects of daily CR versus intermittent CR on weight loss, fat mass loss and lean mass retention in overweight and obese adults. Results reveal similar weight loss and fat mass loss with 3 to 12 weeks' intermittent CR (4-8%, 11-16%, respectively) and daily CR (5-8%, 10-20%, respectively). In contrast, less fat free mass was lost in response to intermittent CR versus daily CR. These findings suggest that these diets are equally as effective in decreasing body weight and fat mass, although intermittent CR may be more effective for the retention of lean mass.
© 2011 The Author. obesity reviews © 2011 International Association for the Study of Obesity.

heybales

Here's an interesting read (re different signals we are sending to our bodies):

Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss?
Varady KA.
Source
Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, IL 60612, USA. varady@uic.edu
Abstract
Dietary restriction is an effective strategy for weight loss in obese individuals. The most common form of dietary restriction implemented is daily calorie restriction (CR), which involves reducing energy by 15-60% of usual caloric intake every day. Another form of dietary restriction employed is intermittent CR, which involves 24 h of ad libitum food consumption alternated with 24 h of complete or partial food restriction. Although both diets are effective for weight loss, it remains unknown whether one of these interventions produces superior changes in body weight and body composition when compared to the other. Accordingly, this review examines the effects of daily CR versus intermittent CR on weight loss, fat mass loss and lean mass retention in overweight and obese adults. Results reveal similar weight loss and fat mass loss with 3 to 12 weeks' intermittent CR (4-8%, 11-16%, respectively) and daily CR (5-8%, 10-20%, respectively). In contrast, less fat free mass was lost in response to intermittent CR versus daily CR. These findings suggest that these diets are equally as effective in decreasing body weight and fat mass, although intermittent CR may be more effective for the retention of lean mass.
© 2011 The Author. obesity reviews © 2011 International Association for the Study of Obesity.

That is interesting.

I love even on this study setup though, why such a big reduction of calories? 15% not so back of course, but up to 60%! Good grief. No wonder the normal days made up for that.

Why can't they just do a test with a nice 20% reduction to true maintenance level? Spend a week with someone else logging everything they eat so that mere act doesn't change their eating level artificially, and then 20% off that?

That would probably leave it above BMR in these kinds of cases.

Though, there have been plenty of people on these forums reporting they upped their calories by 400-600, and lost the same amount weekly, so I guess that actually proves what is possible. But I'd love to see the LBM aspect of it.
Especially with our without exercise when you have a reasonable deficit.

CassieReannan

My BMR is 1900 and MFP reccomends 1400 a day for me to lose 1kg a week without exercise.
Why would MFP reccomend me 1400 if it wasnt safe?

nz_deevaa

My BMR is 1900 and MFP reccomends 1400 a day for me to lose 1kg a week without exercise.
Why would MFP reccomend me 1400 if it wasnt safe?

Because MFP is a computer program that doesn't use BMR in it's calculations.

Here is a quote from earlier in the thread that explains it way better than I could:

MFP calculates the deficit not from BMR but from total energy expended in daily activities.

For a sedentary person, total energy expended on daily activities is estimated as BMR x 1.25.
For a lightly active person, total energy expended on daily activities is estimated as BMR x 1.35.
For an active person, total energy expended on daily activities is estimated as BMR x 1.45.
For an extremely active person, total energy expended on daily activities is estimated as BMR x 1.55

So for a sedentary person who wants to lose a pound a week, MFP sets the net calorie goal to (BMR x 1.25) - 500. (Except it never sets the net calorie goal lower than 1200.)

MFP never sets your net calorie goal lower than 1200 cals for a female.

I lost 20kgs at 1200 calories, but then I stopped losing weight and my hair started falling out.

At Christmas I when I went home on holiday I didn't count my calories, and it felt good.

When I got back from my three week holiday I started reading about BMR and TDEE and decided to put my calories up.

I lose just as much weight each week.

If you have plenty of weight to lose, and you are happy on 1200 calories, keep at it. If you stop losing weight and you start feeling tired all the time and dizzy.... put your calories up.

treetop57

My BMR is 1900 and MFP reccomends 1400 a day for me to lose 1kg a week without exercise.
Why would MFP reccomend me 1400 if it wasnt safe?

For someone your height and weight, my amateur opinion is that 1 kg a week is a reasonable goal to start. But as nz_deevaa points out, you may hit a plateau, at which time you may have to consider reevaluating. Most of the talk about "you must eat more than your BMR" is in response to people who have been on a restricted calorie diet for weeks or months and find themselves on a plateau. It's also usually directed at people who have less to lose than you do.

As nz_deevaa points out as well, MFP is a purely mathematical computer program that spits out a number based only on the numbers you provide it. They explicitly say they are not providing medical advice.

I would quibble with your statement that MFP is recommending 1400 calories. In fact, when you choose a 1 kg/week goal, you are overriding MFP's recommended loss rate of 0.5 kg/week (~ 1 pound per week).

I've got mine set to pounds/inches, so here is what the goal calculator says:

Lose 1 pound per week - RECOMMENDED

I assume yours said:

Lose 1/2 kg per week - RECOMMENDED

Littlerunner0514

bump

melissa2807

I always see it as the following:

BMR = requirements needed to just survive but do nothing
TDEE = requirements to go about your daily business (will change depending on whether you have a desk job or a physical job, or whatever.
If you eat more than your TDEE, you will eventually gain wait because the extra gets stored. Your deficit needs to be below your TDEE but above your BMR.

whiteshadow10189

If you want to lose pure fat and no muscle, do not eat below your BMR. "Weight" may come off slower, but it will be the right type of "weight" and you will look leaner and more toned instead of just a smaller version of what u were before you lost weight.

kaervaak

There is a maximum amount of fat that the body can lose at once, anything over that will be lean mass - Lyle Mcdonald had an article but I can't link from my phone, but will find it later if you haven't found it first.

That's the first piece of info I've seen that makes this make sense. I'd like to find that article.

Agreed. I would like to see it too.

Here is the article: http://www.ncbi.nlm.nih.gov/pubmed/15615615

With a summary from Reddit:

Finally, we need to figure out how much of a calorie deficit you can run, in order to lose weight. To do so, note that you can lose about 31 calories worth of fat per day, per pound of fat in your body, without depleting muscle. (Source: SS Alpert, J Theor Biol. 2005 Mar 7;233(1):1-13.)[http://www.ncbi.nlm.nih.gov/pubmed/15615615[2] ]. For our example, they had 18% bodyfat at 200lbs, which is 36lbs of fat; which means our example person can run a calorie deficit of 31 calories/lb of fat * 36lbs fat = 1120 calories. Subtract this from the BMR (in the example, 2970 calories), and that is the calorie intake per day at which you will lose fat, but should not lose muscle. If you cut fewer calories, you'll probably lose fat still, but you could lose even more. If you cut more calories, you'll begin to lose muscle, which, if you're trying to maintain or build strength, is sub-optimal.

I believe the 31 cal/lb of fat/day number has since be revised down to 22 cal/lb of fat/day as well.

shosh413

WHen you guys are saying eating below your BMR are you including exercise??

My bmr is like 1475 but MFP tells me to eat 1240 so I am eating under it...

however i usually eat back my exercises so i end up eating around my bmr anyway... but what if i wasn't exercising?

AbsoluteNG

Sounds bogus to me, I believe its just made up and spread over and over on the MFP forums.

Why would your body attack muscle first instead of fat for energy? That would be quite stupid

I can see it using muscle for protein it needs, but not energy.

I don't believe your BMR is the magical cut off for your body to start eating your muscle tissue, if someone can prove to me otherwise I stand corrected

Correct. Intermittent fasting diets is a good example of your body using fat before muscles as energy. It's not until you hit the teens in bodyfat percentage should worry about muscle loss.

dosmundos

bump

heybales

Sounds bogus to me, I believe its just made up and spread over and over on the MFP forums.

Why would your body attack muscle first instead of fat for energy? That would be quite stupid

I can see it using muscle for protein it needs, but not energy.

I don't believe your BMR is the magical cut off for your body to start eating your muscle tissue, if someone can prove to me otherwise I stand corrected

Correct. Intermittent fasting diets is a good example of your body using fat before muscles as energy. It's not until you hit the teens in bodyfat percentage should worry about muscle loss.

Your body uses fat as predominate energy source in a 24 hr time span already. Calorie wise, not weight wise.

It's what happens during intense energy use where it gets interesting. Doesn't take much moving up the scale of intensity to start burning more glucose calories than fat, until anaerobic.

Glucose stores are limited.

It's really about having enough glucose stores for what is needed for your activity then.

If your liver runs out, but blood sugar must be maintained, and there is no free protein floating around, then muscle will be broken down to convert to glucose. Oh sure you can get some from lactic acid, but the reason that builds up is it's slow and inefficient. Same with some fat conversion, difficult and slow.
Not a lot, doesn't take much to keep blood sugar up. Well, depending on how long and how intense your workouts are.

That all has nothing to do with bodyfat%. You can be obese, and when you go anaerobic, it's just the same as anyone else, carb burning. When you run out of glucose stores, muscle is still faster and easier to convert to glucose than lactic acid of triglycerides.

It is exactly at your BMR? No obviously not, but is there another line to draw in the sand for giving your body the best performance without some expensive tests?

That true BMR level is what your body would like to burn on taking care of required functions. Mostly supply energy to all the cells. Pulling energy out to put it back in is called perpetual motion, and we just don't have that in our body, or we could lose fat by just not eating.

Outside those normal response, if constantly in an underfed state for level of activity, the body knows how to balance things out. BMR energy use can only be reduced so much, then RMR must be reduced to save calories for BMR, the body knows unused muscle takes more energy than anything else, if something is needed to break down, there it goes.
The body will also slow you down from burning as many calories to save some. The body knows how to do adaptive thermogenesis.

Even related to how much fat energy you can supply.

http://www.ncbi.nlm.nih.gov/pubmed/15615615

AbsoluteNG

Sounds bogus to me, I believe its just made up and spread over and over on the MFP forums.

Why would your body attack muscle first instead of fat for energy? That would be quite stupid

I can see it using muscle for protein it needs, but not energy.

I don't believe your BMR is the magical cut off for your body to start eating your muscle tissue, if someone can prove to me otherwise I stand corrected

Correct. Intermittent fasting diets is a good example of your body using fat before muscles as energy. It's not until you hit the teens in bodyfat percentage should worry about muscle loss.

Your body uses fat as predominate energy source in a 24 hr time span already. Calorie wise, not weight wise.

It's what happens during intense energy use where it gets interesting. Doesn't take much moving up the scale of intensity to start burning more glucose calories than fat, until anaerobic.

Glucose stores are limited.

It's really about having enough glucose stores for what is needed for your activity then.

If your liver runs out, but blood sugar must be maintained, and there is no free protein floating around, then muscle will be broken down to convert to glucose. Oh sure you can get some from lactic acid, but the reason that builds up is it's slow and inefficient. Same with some fat conversion, difficult and slow.
Not a lot, doesn't take much to keep blood sugar up. Well, depending on how long and how intense your workouts are.

That all has nothing to do with bodyfat%. You can be obese, and when you go anaerobic, it's just the same as anyone else, carb burning. When you run out of glucose stores, muscle is still faster and easier to convert to glucose than lactic acid of triglycerides.

It is exactly at your BMR? No obviously not, but is there another line to draw in the sand for giving your body the best performance without some expensive tests?

That true BMR level is what your body would like to burn on taking care of required functions. Mostly supply energy to all the cells. Pulling energy out to put it back in is called perpetual motion, and we just don't have that in our body, or we could lose fat by just not eating.

Outside those normal response, if constantly in an underfed state for level of activity, the body knows how to balance things out. BMR energy use can only be reduced so much, then RMR must be reduced to save calories for BMR, the body knows unused muscle takes more energy than anything else, if something is needed to break down, there it goes.
The body will also slow you down from burning as many calories to save some. The body knows how to do adaptive thermogenesis.

Even related to how much fat energy you can supply.

http://www.ncbi.nlm.nih.gov/pubmed/15615615

I was typing on my smart phone earlier so I didn't feel like typing up a whole essay and what I said was only partial truth. I agree with you that your metabolism does slow down if you constantly eat a low calorie diet and it can cause you to lose muscle mass but someone on a VLCD can prevent slowing down their metabolism and muscle loss easily just by exercising. Link below as proof that someone on a VLCD/PSMF diet can maintain muscle mass and burn only fat just by exercising.

http://forum.bodybuilding.com/showthread.php?t=121060001&highlight=psmf

ppolizzi

I've actually been wondering about this myself. I did a test last spring where I ate 1400 calories a day for about a month straight. My BMR at that time was around 1600. The goal was to see if I could gain muscle mass on a low calories diet and it was successful, I felt great actually! I did increase my calories a bit later because my level of physical activity went up and I frankly was hungry.

Just don't worry! as long as you are feeling good that's all that really matters.

Gee_24

Ok let me give my own "scientific " evidence. I only got a couple of pages in before I got p*ssed off. haha So many people are fighting this and wanting the evidence, but from my own experience I know its true in some form.

I ate about 500-1000 ( Bmr 1100 ) calories a day for the majority of 2009. I went down from 9.5 to 6 stone. I gained it all back within 2 months of eating modestly and could not for the life of me what had gone wrong. I wasn't calorie counting back then but I can assure you I was eating well under 1600 cals a day when I started gaining. I now feel my metabolism was shot to hell via lack of muscle mass. I was only having cups of tea and 1 large meal a day, no snacks.


I have now eaten 1200-1800 calories a day for 4 months, I am 6.3 stone and am a size 4...where as eating below BMR for so long in 2009, I was nearly half a stone lighter and a size 6.

I was skinny - fat. My body was clearly burning way more muscle than fat. I had bones protruding everywhere but fat jiggles all over the place at the same time.

Losing the weight at a far more modest deficit, it has stayed off and I have tonnes more muscle, despite lack of exercise. Oh, and my hair fell out. My nails broke off, I stopped going to the toilet, my periods changed, and my skin was grey. Eating below BMR stops the normal functions of so many things, because your body has no energy to do these basic things for you any more.