Another reason to only eat back half of exercise calories

SherryTeach

As a little experiment this evening, I used my Polar HRM to measure my calorie burn on my treadmill: 41 minutes @ 3.7 mph w/ 1.5% incline=233 calories. I then flopped on the bed with my laptop, restarted the HRM and did not get up for 41 minutes=96 calories. It was disappointing to discover that the net effort of "exercising" isn't as much as you might think. In other words, good for health and fitness, but not a reason to eat more.

MeanderingMammal

Most of that 96 calories would be as a result of using the HRM inappropriately. Your actual calorie expenditure in 41 minutes might have been about 40 calories.

mwyvr

Sherry, while that's an interesting experiment, your Polar device wasn't measuring your calorie burn while at rest. It wasn't designed to do that. We can't possibly know what Polar's software designers were thinking there.

You can figure out for yourself what your at-rest base metabolic rate for those 41 minutes. Divide your daily BMR by 1440 (number of minutes in the day) and multiple by 41. You can use MFP's BMR calculator as a starting point:

http://www.myfitnesspal.com/tools/bmr-calculator

I get 46 calories burned in that period of time at rest. About 1/2 an apple.

If you want to create a larger deficit using the treadmill, in the same amount of time, you've got to move your body over more distance and that means walking faster or running. Jack up your pace to 5 or 6 miles per hour and you'll about double your example calorie burn.

If I run for approximately 41 minutes, according to my Garmin log (runs between 40 and 45 minutes) I'm burning between 500 and 640 calories depending on pace; pace determines distance travelled. Elevation gain also factors in but is a smaller influence overall.

That's an entire larger meal for me or quite a few half apples. I'm not exercising so I can eat more, but there are times when I appreciate it[1]. I eat back the bulk of my exercise calories but save some as a reserve to cover any intake calorie recording mistakes I might make.

[1] Being more honest, I run for beer.

CyberTone

I would agree with @MeanderingMammal; unless your resting internal body temperature is above 110 degrees Fahrenheit, I doubt you are burning (96Cals/41min) = 2.34Cals/min at rest.
Using my stats (53yo, 5'9", 153lbs.), my BMR is 1530Cals/day. So 1530Cals/day x (1day/1440minutes) = 1.0625 Cals/min. My resting Calorie burn for 41 minutes is about 41min x (1.0625Cals/min) = 43Cals.

999tigger

Putting the misuse of technology aside, then why would this be a reason to eat only half back? The only issue and why this half back policy started is because of the tendency for MFP to be overgenerous on calorie burns for some people or for some people to exaggerate their own effort. The aim is to avoid eating calories you havent burned.

If you were to go faster or went for longer then you would burn many more calories. It still takes a lot of exercise to burn substantial calories if that was your aim.

msf74

Are you making the point about net calories burned whilst exercising?

So, say you burned 600 cals an hour while exercising, given you would have burned say 200 cals in the same time being sedentary, the actual contribution towards a calorie deficit is smaller than imagined at 400 calories?

SherryTeach

You are absolutely correct. Upon reflection, 96 calorie burn in 40 minutes would mean that my BMR is 3,456. Since I'm 60 years old, 5'1" and 105 pounds, that is in no way correct. I would like to learn more about how my HRM is calculating exercise calories and why, exactly, it isn't measuring calories for non-cardiac activities since it is still measuring heart rate. But, yes, I would like to be working out a little harder.

SherryTeach

It had been a while since I used a BMR calculator so I'm trying out a few different sites: 984 on one and 988 on another. So I really burned 27 calories in 40 minutes. I wonder if I'd burn more by reading the crazy political rants of my high school FB friends? Well, thanks for the sage and experienced advice here.

annaskiski

My Apple Watch reports 'total', 'active' and 'resting' calories. (total = resting + active)
The 'total' calories are what MFP and my old Polar used to count for my workouts. (MFP meaning, I manually added the workout)
The watch only adds into MFP the 'active' calories now. It ends up being a little more than half of the total calories.

I think you are correct in that some HRMs are reporting your total burn, some of which should not be eaten back, since they are already included in your daily calorie total.

mwyvr

SherryTeach wrote: »

I would like to learn more about how my HRM is calculating exercise calories

From what I've read, from a calorie expenditure perspective devices like Polar and Garmin are designed around calculating burn based on steady state cardio exercise (which is why they aren't that useful in the weight room) and the algorithms are generally tweaked for running.

Different makers and devices *do* handle BMR (leave it in / take it out) differently. From what I gather *my* device does not include BMR calories when it reports exercise calories; this is apparently not true for all (mostly older now) Garmin running watches. It'd be good to know how your particular device handles BMR but may not make difference to you in the end.

For me BMR is ~67 calories per hour and I'm a 54 year old 180 pound male. My running burn rate is 10x that; if my net active calories for a 1 hour 6 or 7 mile run are 667 or 600, that delta won't change what I eat by much, if anything given the delta is less than 1 apple's worth of calories.

Jruzer

To make the calculations simpler I overestimate a baseline burn (TDEE-EAT) of 28800 kcal/day, which conveniently works out to 2 kcal/minute. Then I subtract 2 kcal for every exercise minute regardless of intensity. This to me makes more sense and is more consistent than "eating half back", but to each their own.