Calorie Deficit Calculator
Find your exact daily calorie target for fat loss and see a realistic timeline to your goal weight. Based on your TDEE and a sustainable, evidence-based deficit rate.
Calorie Deficit and Weight Loss Guide
The Energy Balance Equation
Weight change is determined by the balance between energy consumed (calories eaten) and energy expended (TDEE). To lose weight: calories in < calories out. 1 kg of body fat contains approximately 7,700 kcal. A 500 kcal/day deficit produces approximately 0.5 kg fat loss per week. However: early weight loss also includes water and glycogen; initial losses are faster than 0.5 kg/week. Metabolic adaptation: extended calorie restriction reduces TDEE by 10-15%, which is why progress slows over time. T
The Minimum Effective Deficit
Larger deficits do not always produce faster fat loss in practice. Below approximately 1,200 kcal/day for women and 1,500 kcal/day for men: significant muscle loss, nutrient deficiencies, metabolic adaptation, fatigue, poor adherence, and rebound eating are common. Research consistently shows that a 500-750 kcal/day deficit produces the best combination of fat loss rate, muscle preservation, and long-term adherence. Very low calorie diets (under 800 kcal) should only be undertaken under medical
Protein and Muscle Preservation
During a calorie deficit, eating sufficient protein is critical to preserve lean muscle mass. Without adequate protein, the body uses muscle tissue for energy — reducing metabolic rate and producing a less favourable body composition. Target: 1.6-2.2g protein per kg bodyweight during a deficit. For a 85 kg person: 136-187g protein per day. High protein also improves satiety — protein is more filling per calorie than fat or carbohydrate. Research shows that calorie-equated diets with higher prote
Diet Breaks and Reverse Dieting
Metabolic adaptation: after 4-8 weeks of a calorie deficit, TDEE decreases by 10-15% due to reduced body mass (less to move), reduced thermogenesis, and hormonal changes (lower leptin, higher ghrelin). Diet breaks: periods of 1-2 weeks at maintenance calories restore hormones, improve adherence, and partly reverse metabolic adaptation — without regaining fat. Research supports alternating 2 weeks deficit with 1-2 weeks at maintenance for long-term success. Reverse dieting: very gradually increas
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