Key facts
- The fundamental requirement for losing body fat.
- A deficit of ~300–500 kcal/day is a sustainable rate for most.
- Higher protein and resistance training preserve muscle in a deficit.
- Roughly a 7,700 kcal deficit equals about 1 kg of fat lost.
Fat loss obeys energy balance: to lose fat you must take in less energy than you expend, so your body taps its stored energy (mainly fat) to make up the difference. No food or training trick bypasses this — it is the one shared mechanism behind every diet that works.
The practical key is finding a deficit you can sustain. A deficit of around 300–500 kcal per day loses fat at roughly 0.25–0.5 kg per week, which is fast enough to see progress but moderate enough to protect muscle, training quality, and adherence.
To keep the weight you lose as fat rather than muscle, keep protein high (around 1.6–2.2 g/kg of bodyweight) and keep lifting. Resistance training signals your body to hold on to muscle while the deficit strips fat.
Frequently asked questions
How big should a caloric deficit be?
A deficit of about 300–500 calories per day is sustainable for most people and loses roughly 0.25–0.5 kg of fat per week. Larger deficits work faster but are harder to maintain and risk muscle loss.
Can you build muscle in a caloric deficit?
It is possible for beginners, those returning to training, or people with higher body fat (body recomposition), but for most trained lifters muscle gain is slow or stalled in a deficit.
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