The basic mechanism
Your body burns a certain number of calories a day (your TDEE — total daily energy expenditure). Eat less than that and your body makes up the difference from stored energy, mostly fat. That gap is the calorie deficit, and it is the mechanism behind every diet that works, whatever it is called.
Roughly 3,500 calories equals about a pound of fat, so a 500-calorie daily deficit trends toward about a pound a week. It is never that mechanically precise week to week, but the direction holds.
How to get into a calorie deficit
- Find your maintenance calories (our macro calculator estimates this)
- Subtract about 15–25% — usually a 300–600 calorie daily deficit
- Keep protein high to hold onto muscle while you lose fat
- Track your intake so the deficit is real, not assumed — most people underestimate what they eat by hundreds of calories
Why the scale stalls even in a deficit
The most common reason for "I am not losing weight in a calorie deficit" is that the deficit is smaller than you think — unlogged bites, oil, drinks, and weekend meals add up fast. Tracking honestly for a week almost always finds the gap.
Other reasons are normal: water retention (from sodium, stress, hormones, or new training) can mask fat loss on the scale for weeks, and your maintenance calories drift down a little as you lose weight, shrinking the deficit. Judge progress by the multi-week trend, not the daily number.