What MFP does when it calculates your goal

Aaron_K123 Posts: 7,121 Member
edited September 2016 in Health and Weight Loss
Hey all. I was answering someone in an email and wrote up an explanation of what MFP does when it calculates your goal calories. I figured I might want to refer to this for others and rather than retype it it would be nice to just point to a post...so I'm posting it for future reference.

Feel free to correct any mistakes or give actual numbers where I just used examples I made up.


First I thought I'd start with some definitions, you may already know this stuff but just in case.

BMR: Basal Metabolic Rate, the amount of calories your body burns just to keep you alive. If you were in a coma with no activity this is the amount of calories your body would require to maintain its weight.

NEAT: Non-exercise activity thermogenesis: This is your BMR plus the standard stuff people do in their day, like walking back and forth from class in your example. More active people will have higher NEAT, the only thing this leaves out is intentional exercise.

TDEE: Total daily energy expenditure. This is the amount of calories you actually burn in a day. It is your BMR + your activity + calories burned during exercise.

Okay with those in mind the way MFP works is this. BMR is "calculated" by taking into account what you tell MFP about your height, weight and gender. I don't know exactly what formula MFP used but regardless it either goes to a lookup table of what most peoples BMR is with those stats and gives you that number or it uses some formula based on data from a standard population. Its not guaranteed 100% accurate because it doesn't take into account how much of your weight is fat and how much is muscle or general variations within the population but in theory its close.

With your BMR you then give MFP one extra bit of info which is how active you are. I believe MFP then just multiplies your BMR by a factor determined by how active you tell it you are. I don't know what the actual numbers are but to make something up say it multiplies by 1.1 for sedentary, 1.2 for lightly active, 1.3 for moderatly active or 1.4 for active (again made up those numbers they might not be the actual numbers). That is basically your estimated NEAT.

MFP does not inheriently calculate your TDEE. If you exercise you have to tell MFP what you did and then it uses a lookup table to basically guess your calorie burn which it then adds to your calories for the day. If you don't do this it will just use your NEAT.

The final bit of information you give MFP is the amount you would like to lose. If you tell it 1 pound a week then MFP then assumes the following. 1 pound of fat is 3500 calories, therefore to lose 1 pound of fat in one week you need to eat 3500 calories less than your TDEE (MFP uses your NEAT to set your goal). If you need to eat 3500 calories less in a week that is 3500/7=500 calories less per day so MFP takes your NEAT and subtracts 500 and that is your goal. Once again if you exercise you'd need to take that into account so it would be TDEE-500. If you tell it two pounds a week then it would be NEAT-1000 or TDEE-1000 if you add exercise.

That is all MFP does to calculate your goal. In theory if it is accurately reflecting your caloric needs and you accurately enter your caloric intake you will lose weight at the rate that you select. If you exercise you would need to report that and enter in accurate burns to correct for that and apply the same deficit to your TDEE as a net loss.