Exercise calculations

Hi all,

Here's something that has been niggling at the back of my brain ever since I joined MFP, but just now have taken the time to think through. Forgive me if this has already been discussed (probably has) elsewhere and I am rehashing stuff you regulars already know.

In terms of calculating exercise calories, and allowing for extra intake of those calories, we have to calculate the truly EXTRA number of calories we expend other than what the MFP has calculated we burn off in a day of regular activity. We can only "add" the calories we burn that are above and beyond what has already been calculated into our daily allowance.

For example: The number of calories that MFP has calculated that I need for a regular day's living is 1900 calories, based on my age, weight and level of general activity (light).

Let's say that when I am sleeping, I expend about 60 cal/hour and when I am awake I expend about 90 cal/hour. If I sleep 8 hours, then I expend 60 x 8 = 480 calories while sleeping.

That leaves 16 waking hours x 90 = 1440 calories I expend while awake.

Total calories = 1920 (close enough for illustrative purposes).

OK, so when I walk very briskly at 4.0 mph for 60 minutes, that equals 330 calories expended.

But I should NOT consider that I can take in 330 extra calories to maintain the intake/output balance I am shooting for. I need to subtract the number of calories that I WOULD have expended if I had not gone for that walk from the amount of calories I DID actually expend on the walk. This would be 330 - 90 = 240 extra calories.

Unfortunately, when MFP adds in calories expended through exercise, I believe they add the gross calories expended (330) not the net calories expended (240). Correct me if I am wrong here. But if that is what they are doing, this gives a false impression of our overall calorie goals for the day, in this example, 90 calories extra that I did NOT expend.

Anyone with thoughts about that? I guess I just need to calculate this for myself and discount 90 calories for every hour I exercise to get a truer extimate of my input/ output.

Cheers,
Mary

Hm, that's interesting, to deduct BMR calories. That undoubtedly puts you closer to the real expenditure.

So in my example, my BMR is 1200 calories per day. That is about 52 calories per hour. So I would subtract 52 calories from the 330 I expended walking for an hour at 4 mph. The net expenditure would be 278.

I think I'll probably still calculate it the way I describe above, because I would normally expend more than my BMR calories during waking hours, including the waking hour that I am walking 4mph. I think (for me) it's better if I err on the side of giving myself fewer calories to work with rather than erring on the side of giving myself too many calories and thus fooling myself into thinking I'm doing better than i am.

Believe me! I am not one of those who are in calorie deficit so far that there is an issue of the metabolism slowing down!

Thanks all