Should I eat my calories burn?

Let's say you burn 1500 calories a day just living and walking the dog. MFP has calculated this from your height, weight, age and activity level, just as you entered it. You get up, you live, you sleep, and your body burns 1500 calories over the course of that day.

You want to lose weight, so you tell MFP you want to lose a pound a week.

MFP says eat 1200 calories a day.

You are now eating 300 calories less than you are burning. This is called a calorie deficit. You will lose weight by eating 1200 calories a day and carrying on your normal life. You are just eating slightly less than you use in your day to day life.



Oops, you now play two hours of tennis. You burn 500 calories running all over the court.


If you eat 1200 calories, but have burnt 500 calories playing tennis, that only leaves 700 calories for you body to grow your hair, to repair your muscles, to replenish your skin and so on. Your body really needs at least 1200 calories to maintain all those essential functions, but you are not providing your body with those calories.

Your personal numbers will of course be slightly different, but I hope you can understand the principle.