a Question with BMR (perhaps dumb)

snowy0wl

I've been using a lot of measurement devices (bodymedia/polar loop/vivosmart) and they all seem to hover around the base BMR for myself. I am average build but haven't focused on my fitness level till now.

Having closely tracked and beginning a focus on fitness my fat content is dropping considerably even though my diet has been high enough that I'm not starving.

Is it generally true that for people who don't have a medical condition (I'm thinking limited to thyroid) that BMR is pretty close day to day? Barring major illness or drastic changes in diet and damage from past over exercise.

I'm unsure if all these activity devices are just really basically motivators to show you some arbitrary number and aren't really needed if you are focused and have a proper plan.

SideSteel

I'm not quite sure I understand the question.

I would assume that BMR is relatively steady from day to day but TDEE varies significantly for most people from day to day, since TDEE includes exercise activity, non exercise activity, and thermic effect of food, and off of these factors are variable.

But that being said, I would assume you're using your measurement devices to primarily track activity or total energy expenditure and not BMR.

snowy0wl

For bodymedia products it tracks TDEE, but by subtracting exercise times you can arrive at BMR. my exercise is pretty focused and you can see it very clearly in the tracking.

The other fitness band just estimates time.l

I'm still working on understanding how MFP works with the adjustmjent factor in BMR. I keep track using my own spreadsheet and it's working well for me.

My question was more of if BMR when based on muscle mass is pretty much stable person to person unless there is an underling medical condition. It sounds like it is.

and If I'm not clear yes I"m using the devices to track my TDEE although I admit there is a wide range if I start execising. I think when I"m still it can calculate it pretty close
but once you start exercsing it can be way off.

I'd be appreciate peoples input if they use POLAR + Heart rate level and if it's going to be more accurate.

heybales

A woman's BMR can vary by 100-200 calories through the course of the month.

The Katch BMR formula based on Lean Body Mass (not just muscle mass) is actually in the middle of a 5-10 % spread between men and women of equal LBM, because men have bigger metabolic burning organs than women.
http://ajpendo.physiology.org/content/278/2/E308.abstract
Many studies like that.
So if a man and woman had equal LBM, the woman would have more muscle mass or other stuff that's part of LBM, but the man would have bigger burn from the big organs burning most of the calories of the LBM.
So the man would actually have higher BMR.
www.ncbi.nlm.nih.gov/pubmed/1522233

It's also been found that those with African heritage have smaller organs too than caucasians of equal LBM.
So their BMR is smaller than might otherwise be indicated, and that includes the BMR formula using gender, age, weight, height.
http://ajcn.nutrition.org/content/83/5/1062.full

And BMR can also vary depending on your workouts and after-effects. Lifting and intense cardio that does similar damage to muscles can raise BMR while repair is going on for 24-36 hours later to some degree, depending on the intensity of the workout.

Accuracy of HRM formula for calorie burn of steady-state (same HR 2-4 min) aerobic exercise can be improved in devices that have lab measured stats of HRmax and VO2max.
But even there ....
http://www.myfitnesspal.com/topics/show/459580-polar-hrm-calorie-burn-estimate-accuracy-study

You can get close to those lab measured stats with a self-test if you do enough endurance cardio that the difference in calorie burn will matter enough.
Check my profile for a personal calorie burn formula spreadsheet.