Calorie Deficit Calculator

How a deficit produces weight loss

Eating below maintenance forces the body to draw on stored energy. The commonly used figure is that roughly 3,500 calories correspond to about a pound of fat, so a 500-calorie daily deficit approximates a pound a week.

That figure is a useful planning approximation rather than a precise constant — real losses include water and some lean tissue, and the relationship shifts as weight falls.

Sensible deficit sizes

Larger deficits are not proportionally better. Aggressive restriction increases muscle loss, worsens adherence, and tends to produce more pronounced adaptive slowdown.

Intake floors

Going below roughly 1,200 calories a day for women or 1,500 for men is not advisable without medical supervision. Very low intakes make adequate protein and micronutrient intake difficult and increase lean tissue loss.

Why the scale stalls

Weight loss is rarely linear. Water retention from sodium, carbohydrate intake, hormonal cycles and training can mask fat loss for a week or more.

Judge progress on weekly averages over two to three weeks, not day-to-day readings. A genuine plateau lasting several weeks usually means maintenance has fallen with your weight and the deficit needs recalculating.

Protein matters in a deficit

Adequate protein and some resistance training substantially reduce how much of the loss comes from muscle rather than fat. The same deficit can produce quite different body composition outcomes depending on these.

General information, not dietary or medical advice.