How a calorie deficit works
One kilogram of body fat stores roughly 7,700 kcal of energy. To lose that kilogram, you need to consume 7,700 fewer calories than you burn over time. The speed of loss depends entirely on the size of your daily deficit.
A 500 kcal/day deficit produces approximately 0.5kg per week. A 300 kcal/day deficit produces about 0.3kg per week. These are averages — actual results vary based on water retention, sleep, stress, and individual metabolic variation.
What deficit size is right for you?
Gentle (300 kcal/day) — best for people close to their goal weight, beginners, or anyone who wants maximum muscle preservation and minimal dietary disruption. Sustainable indefinitely.
Moderate (500 kcal/day) — the research-backed sweet spot. Produces meaningful fat loss while preserving most lean mass when protein intake is adequate. Sustainable for most people for 12–20 weeks.
Aggressive (750 kcal/day) — appropriate for people with a significant amount of fat to lose. Increases muscle loss risk. Should be combined with high protein intake (2.0–2.4g/kg) and resistance training.
Does the deficit need to be exact?
No. Weekly averages matter more than daily precision. A person who hits a 500 kcal deficit 5 days a week and eats at maintenance 2 days achieves roughly a 360 kcal average daily deficit — still producing around 0.33kg per week. Consistency over weeks and months matters far more than daily exactness.
Why does weight loss slow down?
As you lose weight, your TDEE decreases because a lighter body burns fewer calories. This is why recalculating every 4–6 weeks is important — the same calorie intake that created a 500 kcal deficit at 90kg may only create a 300 kcal deficit at 80kg.
Frequently asked questions
Further reading
If you are eating in a deficit but the scale is not moving, the not losing weight on a calorie deficit article covers the nine most common reasons — including tracking errors, water retention, and metabolic adaptation. For broader context on setting your calorie target, read how many calories to eat to lose weight.