Overestimating Exercise Calories (Gross vs Net)

mike5802

I’m going to try logging my NET calories burned for exercises from now on MFP. This information will be old news to many MFP dieters, and there are many web searches that explore this issue. But, If this is news to you, then you may want to continue reading.

Many of us know that most calorie exercise tables and devices (like pedometers) give GROSS calories burned for a given exercise. Unfortunately, gross exercise calories include BMR calories (like those already pre-calculated by MFP.

For example, my pedometer regularly reports that for my height and weight that I burn about 266 gross calories during my daily 3-mile walk. Again, this number includes my BMR calories.

So, MFP calculates my current daily BMR as 1540 calories. It then adds the 266 gross walking calories for a total adjusted daily goal of 1806 calories. This is an overestimation because it’s double-counting my BMR calories for the walking.

Here is the correct calculation:

At a BMR of 1540 per 24 hours, I’m burning about 64 calories per hour doing nothing. My walk happens to take about an hour, so, in this case, the math is easy. If I back-out the double-counted BMR calories for the duration of my walk, then my daily goal calculation should actually be about 1540 + (266 – 64) = 1734. For each exercise logged, these miscalculations will further overestimate my available goal.

I'm convinced that this is one important reason why dieters counting calories habitually overestimate how many calories they can eat. It's like counting some votes twice in an election!

(Note: this issue is unrelated to the overall “net” calories leftover each day as calculated by MFP).