A calorie deficit is the one thing every fat-loss diet has in common, whatever its name. Understand it and you no longer need the gimmicks.
What a calorie deficit actually is
Your body burns a certain number of calories each day — your maintenance calories, or TDEE. Eat fewer than that and you're in a deficit: your body makes up the shortfall by using stored energy, mostly fat. Eat more and you're in a surplus. That's the whole mechanism. Roughly 7,700 kcal equals about 1 kg of body fat, so a 500 kcal daily deficit loses around 0.45 kg a week.
How big should it be?
Bigger is not better. A moderate deficit of 10–20% below maintenance — usually a 300–600 kcal daily shortfall — is the sweet spot:
- Large enough to lose fat steadily (about 0.5–1% of bodyweight per week).
- Small enough to protect muscle, training performance and your sanity.
Aggressive crash deficits cost muscle, tank your energy and almost always rebound. Work out your target below.
Calorie Target Calculator
- Maintenance (TDEE)
- 2740 kcal
- Daily deficit / surplus
- -548 kcal
Estimated change: -0.5 kg per week.
How to create the deficit
You can eat less, move more, or both — but diet is the powerful lever:
- Build meals around protein and whole foods, which are filling for their calories.
- Keep protein high (around 2 g per kg) to protect muscle — see how much protein to build muscle.
- Use steps and training to spend energy and stay healthy, not to "earn back" food.
Track the trend, not the day
Bodyweight swings daily with water, food and salt. What matters is the multi-week trend. Weigh in consistently, watch the average, and only cut calories further when the trend stalls for 2–3 weeks — because as you lose weight, your maintenance falls too.
This is exactly where data-driven coaching earns its place: our fat-loss programme and nutrition coaching recalibrate your deficit from your real trend, so you keep losing without guessing. Want it done for you? Start with nutrition.