Calorie Deficit

A calorie deficit is the gap between what you spend in a day and what you eat. Spend 2500 and eat 2100 and you are in a deficit of 400 calories.

It is the one mechanism behind fat loss. Every diet that works does so by producing a deficit, whatever else it also claims, and the differences between them are mostly differences in how easy they make it to hold one.

The usual guidance is a deficit of 10 to 20 percent of your total daily energy expenditure, which for most people is 300 to 500 calories and produces something like half a kilogram of loss a week. Larger deficits work faster and cost more muscle, and they are much harder to sustain.

Two things make a deficit shrink without anyone changing anything. Your expenditure falls as you lose weight, because a smaller body costs less to run, and people reliably underreport what they eat by around twenty percent in studies. Both are reasons to judge a deficit by what the scale does over three or four weeks rather than by the arithmetic.

What it is not

It is not a reason to eat as little as possible. Below roughly your basal metabolic rate the cost in muscle, in training quality and in how you feel rises sharply, and the weight lost is a worse kind of weight.

Where you see it in FitnessSyncer

Set a calorie goal and your Dashboard tracks what you ate against it, with your energy spent charted beside it. Our TDEE calculator is where the other half of the sum comes from.