How to use a calorie deficit safely
Fat loss happens when you consistently eat fewer calories than you burn. The size of that gap determines how fast you lose — but also how hungry, tired, and muscle-prone you become. A 15–25% deficit below maintenance is the sweet spot for most adults: fast enough to see progress, slow enough to keep your energy and training intact.
Why this calculator uses percentages
A 500-calorie deficit is perfect for someone burning 2,500 calories per day (20%), but it's a 33% deficit for someone burning only 1,500 calories per day — too aggressive. Percentages keep the diet proportional to your body size and activity level.
Protecting muscle in a deficit
Weight loss on the scale isn't always fat loss. To keep muscle, prioritize protein (0.7–1.0 g per pound of body weight), lift weights 2–4 times per week, and avoid deficits larger than 25% unless supervised.