Exercise Calories: To eat or not to eat... Results

http://www.myfitnesspal.com/topics/show/708037-weight-loss-vs-fat-loss

So the question of whether or not to eat back exercise comes up fairly frequently, so I thought I would try to bring some light to it through statistics (oh yes, I am that nerdy math guy). Above is the thread created to gather information. The goal, was simple, what is better for weight/fat loss.... eating back exercise calories (or eating 20% below tdee) or sticking with the basic number MFP gives you and not eat back exercise calories. Below is what I looked for in order to derive the information

"I am looking for those who can provide starting weight (SW), start body fat (SBF), current weight (CW), current body fat (CBF) and what is your calories. I am trying to compare those who eat exercise calories (this will include those who eat 20% below TDEE) vs those who don't. If possible, I would like to collect 50-100 people if possible so I can make a good conclusion. "

With the above information, I was able to look at weight loss vs fat loss and the associated lean body mass loss. Lean body mass has signifacant purpose. LBM is what determines your metabolic rate (the more muscle you have the higher your metabolic rate, aka muscle burns fat).

" ... However, as a whole, lean body mass is responsible for providing the body with its "essential elements" for proper functioning, as the University of Texas Southwestern Medical Center states. The functions that these "elements" provide include movement, stability, respiration, digestion and immune system responses. However, while lean body mass is essential, body fat is still important..."

With this said, there were 48 people from MFP that were involved in this study. Below is the results

Does not eat back exercise calories

Weight Loss - 56.4
LBM Loss - 13.6
% of Loss - 24%
Max LBM Loss - 70%
Min LBM Loss - 1%
Max Weight Loss - 182.0
Min Weight Loss - 14.2


Eats back exercise calories (or 20% below TDEE)
Weight Loss - 34.1
LBM Loss - 5.0
% of Loss - 15%
Max LBM Loss - 45%
Min LBM Loss - 0% <-- there were several people who gained lean body mass but I will choke some of that up to calculation error.
Max Weight Loss - 104.5
Min Weight Loss - 1.0


So on average, a person will loss 9% more weight from lean body mass. But the thing that is astonishing is the difference between the min max levels. Some people lost as much as 70% of their weight from lean body mass. Additionally, about 66% of the people who did NOT eat back exercise calories lost 25%+ of their weight from lean body mass. Adversely, about 27% of those who ate back exercise calories lost 25%+ of their weight from lean body mass. I dont know about you, but that is pretty significant (39% difference).

So I hope this helps.. based on this, I would suggest eating exercise calories. The main benefit of it is preserving lean body mass, which will not only help maintain your metabolism but it will also fill out your skin and provide greater definition (see two links below)

http://www.nerdfitness.com/blog/2011/07/21/meet-staci-your-new-powerlifting-super-hero/

http://www.myfitnesspal.com/topics/show/392784-skinny-fat-vs-fit-photo?hl=skinny+fat+vs

Hope this helps you make your decision.