How much of a calorie deficit do I need to lose weight?
1 kg of fat contains approximately 7,700 kcal. To lose 0.5 kg/week, create a 550 kcal/day deficit; to lose 1 kg/week, a 1,100 kcal/day deficit. Most guidelines recommend no more than 500–750 kcal/day for sustained fat loss, targeting 0.5–0.75 kg/week. Start by reducing your TDEE by 20% — for someone with a 2,500 kcal TDEE, that is 2,000 kcal/day. Exceeding a 25% deficit increases the risk of muscle loss, nutritional deficiencies, and hormonal disruption.
Is a larger calorie deficit better for faster fat loss?
Very large deficits (>750–1,000 kcal/day) produce faster weight loss initially but cause significant muscle loss alongside fat, slow metabolism through adaptive thermogenesis, elevate cortisol, suppress thyroid hormones (T3), and dramatically increase rebound weight gain risk. Research (Hall et al.) shows that slow, moderate deficits preserve lean mass far better. For most people, 0.5–1% of body weight per week is the sustainable sweet spot for fat loss.
How many calories surplus do I need to build muscle?
A "lean bulk" typically requires a 200–400 kcal/day surplus above TDEE. Beginners (less than 1 year of training) can gain 0.5–1 kg of muscle per month; intermediates (1–3 years) gain roughly 0.25–0.5 kg per month; advanced trainees may gain only 1–2 kg per year. A surplus above 500 kcal/day mostly adds fat. Pair any surplus with progressive overload resistance training and 1.6–2.2 g of protein per kg of bodyweight for optimal muscle gain.
What is the minimum number of calories I should eat per day?
Going below 1,200 kcal/day (women) or 1,500 kcal/day (men) for extended periods risks nutritional deficiencies, muscle loss, gallstones, electrolyte imbalances, and metabolic slowdown. Very low calorie diets (VLCDs) of 800 kcal/day are sometimes used medically under supervision. For sustainable fat loss, it is better to increase your TDEE through exercise (which widens the gap) than to cut calories below these thresholds.
How do I know if my calorie deficit is working?
Track your weight daily (preferably the same time each morning) and calculate a 7-day rolling average — this smooths out daily fluctuations from water retention, sodium, and hormones. Expect 0.25–0.75 kg of weight loss per week on a 250–500 kcal deficit. If the scale is not moving after 2 weeks, either reduce intake by 100 kcal or add 100 kcal of exercise. If losing more than 1 kg/week, increase calories by 100–200 kcal to protect muscle mass.