Calorie Deficit & Weight Loss Timeline Calculator
Calculate your expected weight loss timeline from a specific daily calorie deficit. Includes metabolic adaptation adjustment and realistic rate limits.
Weight Loss Calorie Deficit Guide
The Calorie Deficit Principle
Body fat stores approximately 7,700 kcal per kilogram (3,500 kcal per pound). A 500 kcal/day deficit creates a 3,500 kcal weekly deficit → approximately 0.45 kg (1 lb) per week fat loss. A 1,000 kcal/day deficit → approximately 0.9 kg/week. This 'rule' is a useful starting approximation but is not perfectly accurate because: composition of weight lost changes (water, glycogen, muscle, and fat), metabolic rate adapts downward as weight is lost, the calorie content of body tissue varies. Actual we
Safe Rate of Weight Loss
NHS and NICE guidelines recommend losing weight at 0.5-1 kg per week as safe and sustainable. This requires a 500-1,000 kcal daily deficit. Losing faster than 1 kg/week: significant risk of muscle loss alongside fat — especially without strength training and high protein intake. Metabolic adaptation increases: the body reduces TDEE by more than expected from weight loss alone (adaptive thermogenesis). Very low calorie diets (VLCDs, < 800 kcal/day): medically supervised only. Initial rapid loss (
The Plateau Problem
Weight loss almost always slows over time. Reasons: lighter body burns fewer calories — a 10 kg weight loss reduces TDEE by approximately 70-100 kcal/day. Adaptive thermogenesis: NEAT (non-exercise activity thermogenesis) decreases — fidgeting, spontaneous movement, and general activity reduce as you become lighter and potentially more fatigued. Metabolic adaptation: hormones (leptin, ghrelin, T3) shift in ways that reduce TDEE beyond what weight loss alone would explain. Managing plateaus: redu
Protein and Muscle Preservation
During a calorie deficit, adequate protein is critical to minimise muscle loss. Recommendation: 1.6-2.4 g protein per kg of body weight per day (higher end during aggressive deficit or when exercising). Example: 90 kg person: 144-216g protein/day. Protein has a higher thermic effect (25-30% of calories consumed are used in digestion) compared to fat (2-3%) and carbohydrate (6-8%) — making high-protein diets slightly more effective than predicted by calories alone. Resistance training during a de
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