A calorie deficit means you consistently eat fewer calories than your body uses. Over time, this prompts the body to draw on stored energy (mostly fat) to make up the difference. A commonly used starting point is a deficit of about 300–500 calories per day, which research associates with a gradual, sustainable loss of roughly 0.5–1 lb per week. Larger deficits are harder to maintain and can increase muscle loss. You can create a deficit by eating slightly less, moving more, or both. Combining a modest dietary change with activity tends to be the most sustainable.
Key facts:
- Deficit = intake < total daily burn
- ~3,500 kcal deficit ≈ about 1 lb of fat (common estimate)
- 300–500 kcal/day deficit → ~0.5–1 lb/week
- Combine diet + activity for sustainability