Eating Back the Exercise Calories

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L_Master
L_Master Posts: 354 Member
in Health and Weight Loss
I know this gets discussed alot. I'm still slightly lost.

I see many recommendations from people suggesting things like eating back 50% of ones exercise calories, and struggling to understand why, unless it's some sort of 'insurance policy'.

As I understand it, MFP uses your age/weight/height to make an estimate of TDEE, with the notable exception of EAT. I've heard of some people setting MFP to a certain activity level based on their exercise (i.e. active because they walk on the treadmill for an hour most days), in which case not eating back exercise calories makes sense.

Assuming you use MFP settings for your daily lifestyle routine, sans exercise, it seems like eating back exercise calories is a really bad idea:

Let's say you plug in the numbers, and want to lose 2lbs a week, 1000kcal/day deficit. You select sedentary and get back a number saying you should eat 1000kcal day. Presumably this means on a sedentary day MFP expects you to burn 2000kcal.

Now, if you go out and ride solid on the bike for 2 hours and burn an additional 2000kcal that would make the actual TDEE for the day 4000kcal. However, if you ate back only 50% of exercise cals, you would eat the 1000kcal given by MFP, and half of 2000kcal, so an additional 1000kcal from exercise. This would lead to 2000 kcal IN and 4000 kcal out giving a massive 2000kcal deficit per day.

That's an awful lot of weight to be losing, and I know within a day I'd be absolutely ravenous and within 2-3 days my training would go to absolute worthless...if I could even train at all.

So basically what I'm asking is:

1) Is my understanding of MFP just totally warped?

If not:

2)What are the assumptions being made about MFP usage to justify the idea of eating back anything less than 100% exercise calories.

Replies

  • kami3006
    kami3006 Posts: 4,978 Member
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    The common recommendation for eating back a portion of exercise calories is due to the difficulty of calculating exercise calorie burns. Many folks find MFP's burns to be inflated. So eating a percentage is for leeway in case of errant burns. Ideally, you would eat all of those calories and that is how MFP is designed.

    FWIW, have always eaten all of my exercise calories after a few weeks of nailing down what they actually are and lost at the exact rate I had planned to and am maintaining the same way.
  • 3dogsrunning
    3dogsrunning Posts: 27,167 Member
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    I started out following MFP with a grain of salt and lost as I should - as in logged all my exercise and ate all those calories.
    However, I primarily ran with some weight lifting.

    Some of the estimates on MFP are pretty decent. No method of estimation is perfect, MFP is no different.

    However, some of the estimates on MFP are questionable at best. Look at Ellipitical. It gives no distinction for resistence, intensity, etc. The estimates are quite high, pretty much similar to running in some cases. Elliptical is about half the METs of running.

    This is a good blog about it.
    http://www.myfitnesspal.com/blog/Azdak/view/estimating-calories-activity-databases-198041

    Basically, yes, you should follow MFP but not blindly.
    Then again, no method should be followed blindly.

    And this isn't even getting into the issue of what to log or not log. Lots of people log a lot of activity, ending up with huge calorie burns, then can't figure out why they aren't losing weight.

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