How Does Myfitnesspal Calculate BMR?

cosmo_momo

This semester I am taking a 300 level animal nutrition class. I am in the honors section so once a week we meet (6 students and our prof) and discuss research articles from dairy science, animal science, and/or journal of nutrition. While we don't specifically ONLY discuss human nutrition, much of it is applicable. A few weeks ago we discussed an article about basal metabolism and heat increments in growing farm animals. This got us on the subject of calories.

We talked about Kleiber's Law (is the observation that, for the vast majority of animals, an animal's metabolic rate scales to the ¾ power of the animal's mass.) We talked about an equation to find anyone's BMR. That equation is ((weight in kg)^0.75)x(77calories). According to this, my BMR would be 1,799.54 calories/day.

I'm actually pleasantly surprised to see that myfitnesspal calculates that if I want to maintain my current weight, with a sedentary lifestyle, I should aim for 1,780cal/day. I actually started this thread with the intention of asking a question, but at this point I have answered it for myself. I felt that the 1,280 calories for 1lb. a week weight loss was far too low. Now I understand exactly where it's coming from so now that I've rambled on about this, I'll just leave it here for anyone that's interested.

http://universe-review.ca/R10-35-metabolic.htm <-- this is a good scholarly article explaining Kleiber's law in detail for anyone that wants to nerd out and read it

socioseguro

Thank you for sharing

WalkingAlong

MFP uses the Mifflin-St. Jeor BMR equation. You can see it here:
http://en.wikipedia.org/wiki/Basal_metabolic_rate

It uses your weight, height, age and gender, unlike your formula above that just uses weight.

Technically speaking to lose one lb. a week you probably wouldn't be told to eat 1280 if your BMR was 1780 because even sedentary people burn around 1.2 times BMR in a day. I'm not positive if MFP uses 1.2 as the multiplier for 'sedentary' but that's what most sites use. I've never seen a site subtract from BMR alone (with no activity calories considered).

squirrlt

@cosmo_momo‌ I see your 3/4 power is based on Kleiber's law, but where did you get your 77 calorie multiplier? Sorry I only skimmed the article, I'm on a phone.

TwelveSticks

Miffin St Jeor has mine at 1771, which is about right - if I do absolutely no exercise, I've worked out my TDEE (which is near enough the BMR in those circumstances) is around 1750.

The equation given by the OP would have my BMR as 2224, which is way too much for me.

cosmo_momo

@squirrit that number was one our prof told us, I recall him saying where it was from but I'm still working on figuring that out. We don't have a textbook and we don't have exams for that 1hr honors credit so I don't take many notes. I will find out though!

StaciMarie1974

((weight in kg)^0.75)x(77calories) for me comes out too high to be my BMR, but about what I'd burn per day being fairly sedentary. I say fairly, because if I'm really sedentary I might only burn 1500 - and this comes out to 1591.

cosmo_momo

Maybe I am confusing BMR with something else...

cosmo_momo

WalkingAlong wrote: »

MFP uses the Mifflin-St. Jeor BMR equation. You can see it here:
http://en.wikipedia.org/wiki/Basal_metabolic_rate

It uses your weight, height, age and gender, unlike your formula above that just uses weight.

Technically speaking to lose one lb. a week you probably wouldn't be told to eat 1280 if your BMR was 1780 because even sedentary people burn around 1.2 times BMR in a day. I'm not positive if MFP uses 1.2 as the multiplier for 'sedentary' but that's what most sites use. I've never seen a site subtract from BMR alone (with no activity calories considered).

Thank you for telling me what myfitnesspal uses. I was unaware and should have looked into that before posting this :P. Is there a reason that my numbers using the two different equations were so similar and yet other's are very different? I'm using 147lbs (66.8kg) as my weight.

erickirb

Maybe the calculation was for maintenance, then it sounds about right for most of the people that posted. BMR is the amount of cals your body would consume to maintain your weight while in a coma, didn't move or eat, or sit up, etc.

cosmo_momo

erickirb wrote: »

Maybe the calculation was for maintenance, then it sounds about right for most of the people that posted. BMR is the amount of cals your body would consume to maintain your weight while in a coma, didn't move or eat, or sit up, etc.

This!! Sorry you are correct in saying maintenance. I have incorrectly used BMR for describing this equation.