How big should your calorie deficit be?

A sustainable calorie deficit for most people is 300–750 kcal per day below maintenance, with 500 kcal per day being a reasonable middle point that typically produces about 0.5 kg (1 lb) of fat loss per week. This range is large enough to lose weight consistently, yet small enough to preserve lean mass, maintain energy for training, and stick with over months.

Why a moderate deficit works better

The arithmetic of weight loss is simple: burn more than you eat and your body draws on stored energy. The 7,700 kcal per kg rule (the energy density of adipose tissue) means a 500 kcal daily deficit should yield about 0.5 kg per week. But the body does not behave like a spreadsheet, and a larger deficit does not buy you faster results — it buys you more problems.

At very low intakes, the deficit starts to erode lean muscle along with fat. Research on athletic populations shows that protein needs rise in a deficit (toward 1.6–2.0 g/kg of body weight for people who exercise regularly, per the ISSN position stand), and even then, deficits beyond about 1,000 kcal per day tend to increase the share of weight lost from muscle rather than fat. A large deficit also raises the risk of fatigue, reduced training quality, and rebound overeating.

Who should stay closer to maintenance

If you are new to training, carry a lot of body fat, or are already lean, the math shifts. Newer lifters can often gain muscle while losing fat at a small deficit or even at maintenance, because the combination of training and adequate protein creates a favorable environment for body-composition change. People with high body-fat percentages (above roughly 25% for men or 32% for women) can tolerate a larger deficit because they have more stored energy to draw on.

Conversely, if you are already at a low body-fat level (below about 15% for men or 20% for women), a large deficit is more likely to erode the muscle you have worked to build. In that situation, a gap of 200–300 kcal per day is often more effective than a large one, because preserving lean mass is the priority.

Protein matters more than the deficit size

Whatever deficit you choose, protein becomes the guardrail. At 1.6–2.0 g per kg of body weight per day, you give your body the building blocks to hold onto muscle while it burns fat. The deficit determines the rate of loss; protein determines how much of that loss is fat.

Use the protein calculator to set your target, and the calorie deficit calculatorto turn a weekly rate of loss into a daily number. For the broader context of how a deficit fits into a full plan, see the TDEE guide and the weight-loss timeline guide.

Limitations

These ranges are population averages. Individual metabolism, medical history, and hormonal factors can shift the safe zone. The deficit numbers are starting points, not prescriptions — adjust based on how your weight and energy change over a two-to-three-week period.

Formulas are estimates, not medical advice.

Sources