Nutrition

How big should your calorie deficit be to lose fat?

A deficit of about 300–500 kcal a day, or losing 0.5–1% of body weight per week, burns fat while protecting muscle, strength and your sanity.

For most people who train, the best calorie deficit is moderate: about 300–500 kcal below maintenance per day, which usually produces a loss of 0.5–1% of body weight per week. That pace is fast enough to see progress on the scale every few weeks and slow enough to keep most of your muscle, your strength in the gym and a diet you can actually stick to.

Why the size of the deficit matters

Fat loss only happens when you take in less energy than you burn, but bigger is not automatically better. A very large deficit increases muscle loss, drains training performance, makes hunger harder to manage and raises the odds that you abandon the diet after a few weeks. Leaner people are hit hardest: someone with little fat to lose has fewer energy reserves, so the body is quicker to break down muscle when food is very low.

A useful rule is to set the rate of loss as a percentage of body weight rather than a fixed number of kilograms:

• 0.5% per week: lean lifters, people close to their goal, anyone prioritising strength


• 0.5–1% per week: most people with a moderate amount of fat to lose


• Up to 1–1.5% per week: people with a lot of fat to lose, usually only in the first weeks

How to set your deficit step by step

• Estimate your maintenance calories (TDEE), for example with an online calculator or by tracking intake and weight for two weeks.


• Subtract 300–500 kcal. For a maintenance of 2,600 kcal, start at 2,100–2,300 kcal.


• Set protein first (about 1.8–2.4 g per kg of body weight), then fill the rest with carbohydrates and fats you enjoy, keeping fat at least around 0.6 g/kg.


• Weigh yourself most mornings under the same conditions and compare weekly averages, not single days.

Adjusting after the first weeks

Ignore the first week: changes in water, glycogen and food volume can swing the scale by 1–2 kg. From week two onwards, compare weekly averages. If you are losing less than 0.25% per week for two to three weeks in a row, reduce intake by another 100–200 kcal or add about 2,000–3,000 daily steps. If you are losing more than 1% per week and your lifts are dropping, add 100–200 kcal back.

Expect weight loss to slow over time. As you get lighter you burn less energy, and daily movement often drops without you noticing. Small, planned adjustments work better than slashing calories in frustration.

Signs your deficit is too aggressive

• Your main lifts fall several weeks in a row, not just on one bad day


• You feel cold, irritable or constantly preoccupied with food


• Sleep gets worse and resting heart rate creeps up


• You are losing more than 1–1.5% of body weight per week after the first month

Keep training heavy

Strength training is what tells your body to keep muscle while you diet. Keep lifting challenging loads with similar rep ranges, and if fatigue builds, cut a few sets rather than the weights. Cardio and steps help increase the deficit, but they work best as a supplement to lifting, not a replacement.

FAQ

Can I lose fat faster with a 1,000 kcal deficit?
You will lose weight faster at first, but more of it is likely to be muscle, and most people cannot sustain it. Save very large deficits for supervised situations.

Should I eat back the calories burned in workouts?
If your maintenance estimate already includes your training, no. Fitness trackers often overestimate exercise calories, so eating them back can erase the deficit.

How long should a fat-loss phase last?
Usually 8–16 weeks, followed by a few weeks at maintenance. Longer phases work too, but planned breaks make them easier to sustain.

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