Step 1: Know your TDEE
You cannot set a calorie deficit without knowing your Total Daily Energy Expenditure (TDEE) — the number of calories your body burns on an average day including exercise. Use our TDEE Calculator to find this number first.
Your TDEE is your maintenance calories — eat this amount and your weight stays roughly stable. Eat less, and you lose weight. The size of the gap between what you eat and what you burn is your calorie deficit.
How big should your deficit be?
| Deficit size | Weekly loss | Safety rating |
|---|---|---|
| 100–250 kcal/day | ~0.1–0.2 kg | ✅ Very safe — minimal side effects |
| 300–500 kcal/day | ~0.3–0.5 kg | ✅ Gold standard — recommended for most |
| 500–750 kcal/day | ~0.5–0.7 kg | ⚠️ Moderate — ensure adequate protein |
| 750–1000 kcal/day | ~0.7–1.0 kg | 🔶 Aggressive — short-term only |
| > 1000 kcal/day | > 1.0 kg | 🚫 Not recommended without supervision |
The 300–500 kcal/day deficit is the most evidence-supported range. It produces consistent fat loss while preserving muscle mass and is sustainable long-term without causing significant hunger, fatigue, or hormonal disruption.
What is the minimum safe calorie intake?
Health guidelines generally recommend no fewer than 1,200 kcal/day for women and 1,500 kcal/day for men. But these are hard floors — not targets. Most people do far better eating at or above their TDEE minus 500 kcal. The floor matters mainly if someone has a very low TDEE to begin with (e.g. a small, sedentary person).
Very low calorie diets (below 800 kcal/day) should only be undertaken under medical supervision. They carry risks of muscle loss, nutrient deficiencies, gallstone formation, and severe metabolic adaptation.
Why bigger deficits often backfire
Cutting calories aggressively seems logical — eat much less, lose weight faster. In practice, large deficits trigger several counterproductive adaptations:
- Metabolic adaptation: Your body reduces TDEE in response to sustained large deficits by lowering activity levels and reducing the energy cost of basic functions.
- Muscle loss: Without adequate protein and a moderate deficit, the body breaks down muscle tissue for energy alongside fat.
- Increased hunger: Large deficits elevate ghrelin (hunger hormone) and reduce leptin (satiety hormone), making adherence increasingly difficult.
- Cortisol elevation: Extreme restriction raises cortisol, which promotes abdominal fat storage — ironically working against fat loss goals.
How to structure your deficit calories
Once you have a calorie target, split it across macros sensibly. The key rule during a deficit is to keep protein high (1.6–2.2g/kg of body weight) and adjust carbs and fat to fill the remaining calories based on preference.
People who train frequently tend to do better with more carbohydrates (for workout fuel). People who find fat more satiating may prefer more fat and fewer carbs. Both approaches work equally for fat loss at matched protein and calories.
How long should you stay in a deficit?
Most people benefit from cutting phases of 8–16 weeks, followed by a maintenance period ("diet break") before cutting again if needed. This prevents excessive metabolic adaptation, gives the body time to recover, and is psychologically far more sustainable than trying to maintain a deficit indefinitely.
If progress stalls — which it almost always does after several weeks — recalculate your TDEE at your new lower weight rather than cutting calories further. As you lose weight, TDEE decreases, so the same deficit becomes smaller relative to energy expenditure.