A pound of body fat is commonly said to contain about 3,500 calories (a kilogram is roughly 7,700). So in theory, a 500-calorie daily deficit loses about a pound a week. It's a useful rule of thumb — but it's an approximation, not a law. Here's what to actually do with it.
Where 3,500 comes from
Body fat stores roughly 3,500 calories of energy per pound. That's why the classic advice is: to lose a pound a week, eat about 500 fewer calories a day (500 × 7 = 3,500). It's the basis of most calorie deficit maths.
Why it's only a rule of thumb
In the real world it's messier:
- Your burn changes as you get lighter, so the same deficit loses slightly less over time (how to break a plateau).
- Water weight swings hide fat loss week to week (why am I not losing weight).
- Some weight lost is water and muscle, not pure fat — which is why protein matters (how much protein per day).
So 3,500 is great for planning, not for predicting your exact weekly drop.
How to use it
- To lose ~0.5kg/week, aim for roughly a 500-calorie daily deficit.
- To lose ~1kg/week, roughly 1,000 — but don't go extreme; faster isn't always better (how to lose weight fast).
- Judge the weekly trend, not the day-to-day scale.
Turn the maths into a habit
forme tracks your calories and protein from a quick scan and updates your target as your weight changes — so your deficit stays on track week after week.
The bottom line
A pound of fat is about 3,500 calories, so a ~500-calorie daily deficit loses roughly a pound a week. Treat it as a planning guide, keep protein high, and trust the weekly trend. This is general information, not medical or dietary advice.