What Is a Calorie Deficit?
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A calorie deficit is the amount by which energy expenditure exceeds energy intake over a period. It describes energy balance; it does not guarantee an exact amount or rate of fat loss.
Estimate a starting value with the Calorie Deficit Calculator.
Formula
calorie deficit = estimated energy expenditure − calorie intake
If expenditure is 2,300 kcal/day and intake is 1,900 kcal/day, the planned deficit is 400 kcal/day. The equivalent energy balance is 1,900 − 2,300 = −400 kcal/day.
Deficit from food, activity, or both
A deficit can arise from lower intake, higher expenditure, or a combination. Exercise estimates are uncertain and can be double-counted when an activity multiplier already includes typical training. The plan should be evaluated over a normal week rather than one day.
Why the scale does not follow the formula each day
Daily scale weight changes with water, glycogen, sodium, food mass, bowel contents, menstrual-cycle effects, and inflammation from training. Fat change is only one component. Use weekly or multi-week trends when appropriate.
Calorie deficit versus low-calorie diet
A deficit is relative to a person's expenditure. The same intake can be a large deficit for one person, a small deficit for another, or maintenance for someone else. A low number is not automatically a better plan.
Common mistakes
- Subtracting a deficit from BMR instead of estimated total daily expenditure.
- Counting the same exercise in both activity level and added exercise calories.
- Treating the 3,500-kcal-per-pound shortcut as a guaranteed linear schedule.
- Changing the target after one high or low weigh-in.
- Ignoring protein, micronutrients, medical conditions, sleep, and adherence.
Sources
Evidence and editorial status
Evidence for this package was checked on September 10, 2026. This material is educational and is not medical diagnosis, treatment, or individualized nutrition advice.
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