Find your daily calorie intake to lose weight at your chosen rate
A calorie deficit occurs when you consume fewer calories than your body burns. Since your body needs energy to function, it turns to stored fat when calories are insufficient — resulting in fat loss. One kilogram of body fat contains approximately 7,700 calories, so a consistent 500-calorie daily deficit produces roughly 0.5 kg of fat loss per week.
| Daily deficit | Weekly fat loss | Sustainability |
|---|---|---|
| 200 cal/day | ~0.2 kg/week | Very sustainable, slow |
| 300 cal/day | ~0.3 kg/week | Sustainable, recommended for most |
| 500 cal/day | ~0.5 kg/week | Good for most people |
| 750 cal/day | ~0.75 kg/week | Aggressive — monitor muscle loss |
| 1000 cal/day | ~1 kg/week | Very aggressive — risk of muscle loss |
Most health guidelines recommend a maximum deficit of 500–750 calories per day for sustainable fat loss without significant muscle loss. Larger deficits accelerate weight loss but also trigger metabolic adaptation (the body reduces TDEE in response to restriction) and increase muscle breakdown, particularly without adequate protein and resistance training.
When you lose weight rapidly, a significant portion of that loss comes from muscle rather than fat — particularly if protein intake is low and exercise is absent. Losing muscle reduces your BMR, making future fat loss harder and weight regain more likely. Studies consistently show that people who lose weight slowly (0.3–0.5 kg per week) maintain a higher percentage of their lost weight after one year than those who lost weight rapidly.
Maintaining high protein intake (1.6–2.4g per kg of body weight) during a calorie deficit is the most evidence-based strategy for preserving muscle. Protein also has the highest satiety per calorie of any macronutrient, making a deficit easier to sustain. A 75 kg person should target 120–180g of protein per day while in a deficit.
Approximately 1,100 calories per day — because 1 kg of fat contains about 7,700 calories, and 7,700 ÷ 7 days = 1,100 calories. However, this is an aggressive target that most people cannot sustain without significant muscle loss. A 500 calorie deficit (0.5 kg/week) is more realistic and sustainable for most people.
Some muscle loss is almost inevitable during a calorie deficit, especially in larger deficits. The main strategies to minimise it: maintain high protein intake (1.6–2.4g/kg), continue resistance training, avoid extreme deficits, and lose weight at a moderate rate. Well-designed cutting protocols in natural athletes typically result in 80–90% fat loss and 10–20% muscle loss.
Common reasons: overestimating TDEE, underestimating food intake (studies show people underreport calories by 20–40% on average), water retention masking fat loss, inaccurate food tracking, or metabolic adaptation. If you have been in a consistent deficit for 2–3 weeks without scale movement, try a 1–2 week diet break at maintenance calories, then resume the deficit.
When you return to eating at TDEE, weight loss stops. If you return to eating above TDEE (your previous maintenance before the diet), you will regain weight. The key to keeping weight off is either maintaining the new lower calorie intake permanently or increasing TDEE through more activity or muscle gain.
Both create deficits, but they work differently. Diet is more efficient for creating large deficits — you can cut 500 calories from food in minutes, whereas burning 500 extra calories through exercise takes 45–60 minutes of vigorous activity. Exercise is superior for health, fitness, and muscle preservation. The optimal approach combines moderate dietary reduction with increased activity.