What's the deal with BMR?

tara_means_star

I've seen people on here say that eating below your BMR doesn't matter and I've seen others say that eating below BMR for extended periods of time can make you stall. I've seen both arguments from long term MFP-ers who seem to be incredibly knowledgeable which is kinda confusing. What are the arguments for both sides of this issue?

ilex70

I'm sure you will get some more detailed answers, but as far as I know eating under your BMR can be fine if you have sufficient calories available from fat metabolism (accessing stored fat), but not a good idea if you don't.

So if you are obese, probably fine. If you are within normal weight range, not such a good idea.

Don't know if this calculator is perfectly accurate, but if you put in your info, including body fat percentage, it will list a number of calories available from fat metabolism.

1percentedge.com/ifcalc/

I used the tape method to guess at lean mass.

fitness.bizcalcs.com/Calculator.asp?Calc=Body-Fat-Navy

Don't know how accurate the method is, but from what I have read most of the body fat impedance type devices aren't any good.

tara_means_star

I'm really interested in this issue from an academic standpoint and personal too. Mostly, I want to understand the science behind the sides.

Thanks for your response...you didn't mention people in the overweight range though. Where do they fall into the issue

MommyL2015

BMR is what your body burns when you are in a total resting state, just to keep you alive, not taking into account any activity at all except basic body functions. It is probably not a good idea to eat under that very often, if ever. I wouldn't want to, because it's generally a low number. Mine is about 1050, according to some calculators but I've never had it tested.

ilex70

Thanks for your response...you didn't mention people in the overweight range though. Where do they fall into the issue

I think that will depend on body fat percentage/total fat mass. I'm only 4 pounds above overweight at the moment and according to the calculator my maximum fat metabolism is 2438. My BMR is 1576.

So theoretically my body could pull my entire BMR from fat metabolism. My TDEE is only 2210.

But I eat 1200-ish and I'm planning to slowly increase that.

scolaris

Are you confusing BMR with TDEE? The first is just the amount a body -- any body -- at your particular age, gender, height, and weight burns doing the most basic functions of breathing, cell turnover, sleep maintenance, brain firing, etc.
Once your feet hit the floor to head for the loo in the morning you have entered the realm of TDEE. That is your BMR + your activity. The most sedentary among us might just sit in front of a screen all day, walk 15 steps to the garage and go buy drive-thru; the most active among us might run an ultra marathon or summit Everest. Most of us fall somewhere between this!
A clinically obese person will have some wriggle room here because their fat mass takes fewer calories to maintain than their lean body mass. So the BMR of their lean body mass is what they would not want to compromise. For everyone else, medical authority seems to agree you really don't want to hamper your body's ability to perform basic functions. And although you would hope in a perfect world your body would only burn fat stores in this situation, the truth is it will cannibalize lean mass as well which is really no bueno.
For me the deal clincher is this: study after study shows people who go to unhealthy lengths to lose weight have some of the poorest outcomes when it comes to weight maintenance. Eating below your BMR isn't helping you cultivate a new healthier relationship with nourishment and it's not a sustainable strategy. So ask yourself 'do I just want to lose weight? or do I want to keep it off?'

tara_means_star

scolaris wrote: »

Are you confusing BMR with TDEE? The first is just the amount a body -- any body -- at your particular age, gender, height, and weight burns doing the most basic functions of breathing, cell turnover, sleep maintenance, brain firing, etc.
Once your feet hit the floor to head for the loo in the morning you have entered the realm of TDEE. That is your BMR + your activity. The most sedentary among us might just sit in front of a screen all day, walk 15 steps to the garage and go buy drive-thru; the most active among us might run an ultra marathon or summit Everest. Most of us fall somewhere between this!
A clinically obese person will have some wriggle room here because their fat mass takes fewer calories to maintain than their lean body mass. So the BMR of their lean body mass is what they would not want to compromise. For everyone else, medical authority seems to agree you really don't want to hamper your body's ability to perform basic functions. And although you would hope in a perfect world your body would only burn fat stores in this situation, the truth is it will cannibalize lean mass as well which is really no bueno.
For me the deal clincher is this: study after study shows people who go to unhealthy lengths to lose weight have some of the poorest outcomes when it comes to weight maintenance. Eating below your BMR isn't helping you cultivate a new healthier relationship with nourishment and it's not a sustainable strategy. So ask yourself 'do I just want to lose weight? or do I want to keep it off?'

No, I'm familiar with the difference between BMR and TDEE. My BMR is somewhere around 1625 (if I've calculated it correctly) and my TDEE is likely somewhere around 2100 (again, if I've calculated it correctly).

bpetrosky

There is no harm from consuming below BMR on occasion, as long as your average intake is sufficient. People who do 5:2 intermittent fasting, for example, do this regularly.

The harm comes when people eat at or below BMR for a sustained period. It is very hard to get all of your nutritional needs met at a very low level, and malnutrition can have many effects on the body.

For weight loss, BMR isn't even the number you need to worry about. TDEE is the more important number. Consume below TDEE and you lose weight, consume above that and you gain it.

tara_means_star

bpetrosky wrote: »

There is no harm from consuming below BMR on occasion, as long as your average intake is sufficient. People who do 5:2 intermittent fasting, for example, do this regularly.

The harm comes when people eat at or below BMR for a sustained period. It is very hard to get all of your nutritional needs met at a very low level, and malnutrition can have many effects on the body.

For weight loss, BMR isn't even the number you need to worry about. TDEE is the more important number. Consume below TDEE and you lose weight, consume above that and you gain it.

Alright, so if my BMR is 1625 like I think it is and I ate on average 1300-1400 calories for a few months, I was being unhealthy? I'm very curious about this 1. as a way to make sure I keep myself healthy and 2. I'm interested in an academic sense.

scolaris

If you have that BMR because you are tall, that is not optimal. If you have that BMR because you were obese then it is probably not so significant because the BMR of your lean body mass lurking in there would be less. But really it is your TDEE that you want to calculate from to lose weight.

bpetrosky

It depends on your current stats, what you are eating, and your activity level. I could not say whether or not you were being unhealthy just from what you state there.

If you eat at 1400/day AND run 5 miles, it's less healthy than if you eat the same level and are sedentary.

nordlead2005

I'm yet to see any research indicating that eating under BMR is bad for you in any way.

There is research showing you need to get your nutrients in. There is research showing your fat can only provide so much energy per day. If you are in the safe range for both of those and that is under BMR and you are happy, then I see no reason to eat more calories just to be above BMR. (as a side note I ate under BMR by 50-100 calories/day for a large portion of my weight loss).

Much like suggestions to keep weight loss under 1% of your bodyweight per week, or 1-2lb/week or only having a deficit up to 20% of TDEE, eating over BMR is a guideline for keeping weightloss safe.

Personally, I feel the BMR guideline is one of the most confusing ones and least useful ones. I think most people are better off following the 1% or less rule or the TDEE - 20% rule and then just monitoring BF% as best as possible combined with making adjustments as necessary.

Sued0nim

BMR is only significant because it allows you to calculate TDEE

You can with care hit your nutritional minimums at around 1200 calories for a woman

Eating under BMR is like eating under your bed..has no impact on your health markers but some people might think you're a little odd

:bigsmile:

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sweetie1975

It was my understanding that eating at your BMR would help you to maintain your weight but if you wanted to lose, then you had to eat below your BMR....not by an extreme amount but maybe 200 calories per day less than your BMR.

tara_means_star

sweetie1975 wrote: »

It was my understanding that eating at your BMR would help you to maintain your weight but if you wanted to lose, then you had to eat below your BMR....not by an extreme amount but maybe 200 calories per day less than your BMR.

You're confusing BMR with TDEE

abatonfan

Isn't BMR your TDEE when you're completely comatose?

TDEE = BMR + additional calories burned during the day (being awake and resting burns more compared to if you're comatose, and you burn more moving than if you're resting, etc). Theoretically, if the additional calories burned is equal to 0 (you're comatose), then TDEE = BMR. In instances of being comatose, if you received artificial nutrition to meet your BMR, you would maintain your weight (CI=CO).

rileysowner

I think if a person is obese, eating below BRM is less of an issue, although, I don't see the point. Eating at BMR will result in weight loss (assuming you fall in with the majority since BMR estimates are based on statistics drawn from testing a fairly large number of people to get averages). Eating below it may increase weight loss speed, but that is not always a good thing as much as most of us would like it. Although the site linked above speaks of "Maximum Fat Metabolism" I am not really confident in numbers like that. Although I have not researched lately, it seems that while we know that the maximum amount of fat a person can oxidize in a day is directly related to how much fat you have on your body, at the same time, the research (at least then) was still unclear on the actual numbers. Add to that, most people who have weight issues have other issues with eating habits and need to learn and establish new ones (I include myself in this group) slower weight loss helps give time to learn and establish those new habits.

While my view when I first started was lose as fast as I can. Now I look and take the approach of eating as much as I can while still having moderate weight loss, at this point 1 pound a week. Eating at my BMR would get me much more than that, but would just keep my disordered patterns of eating going.

The long and short of it, I see no good reason for most people to eat below their BMR.

Sued0nim

abatonfan wrote: »

Isn't BMR your TDEE when you're completely comatose?

TDEE = BMR + additional calories burned during the day (being awake and resting burns more compared to if you're comatose, and you burn more moving than if you're resting, etc). Theoretically, if the additional calories burned is equal to 0 (you're comatose), then TDEE = BMR. In instances of being comatose, if you received artificial nutrition to meet your BMR, you would maintain your weight (CI=CO).

At rest

Comatose is a bit of a misnomer I think

Not that I personally see that great a difference apart from digestion