Glossary
Calorie deficit
Updated 2026-07-01By Chris RichardsAll terms
Definition
A calorie deficit is a sustained gap between energy in and energy out. It is the primary driver of fat loss for most people.
Definition
A calorie deficit occurs when average calorie intake stays below average calorie expenditure. The body covers the gap by using stored energy, including body fat.
How people create one
Reduce intake, increase movement, or combine both. Moderate deficits are usually easier to sustain than extreme cuts.
How to track it
Estimate maintenance, set a target below it, log food, and watch weekly weight trends. Use a calorie tracker to keep the gap visible.
Sources
- [1] Hall KD, Sacks G, et al. “Quantification of the effect of energy imbalance on bodyweight” (2011) — The Lancet 378:826–837 (PMID 21872751)
General nutrition information, not medical advice. Calorie and macro targets are estimates — talk to a doctor or a registered dietitian before changing your diet, especially if you are pregnant, managing a health condition, or have a history of disordered eating.
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