Question: how many calories to eat in a day to not gain weight?
Answer: As a guide, men need around 2,500kcal (10,500kJ) a day to maintain a healthy body weight, and women need around 2,000kcal a day (8,400kJ). If you need to lose weight, aim to lose about 0.5 to 1kg (1 to 2lb) a week until you reach a healthy weight for your height.