How much weight can I lose if I only eat 1500 calories a day? In another study, adults followed a commercial weight loss program that provided either 500, 1,200–1,500, or 1,500–1800 calories per day. After 1 year, those on the 1,200–1,500-calorie-per-day diet experienced an average weight loss of 15 pounds (6.8 kg).Jun 11, 2020