If you are a boy and want to gain weight, you can refer to the diet of bodybuilders. Eat a certain amount of meat every day, even if you don't want to eat it, you should swallow it as medicine. You should exercise for a certain time every day to ensure a certain amount of exercise, because the best way to gain weight is to exercise your muscles first, and then gradually gain weight. You'd better choose equipment to exercise, so that you won't get hurt easily and your muscles won't be messy and ugly because of irregular movements. If it is a girl, it will be easy. You can start with aerobic exercise. You don't need to eat too much meat, but you still need to do regular daily exercise and exercise with equipment. Because girls are fatter than boys, you must control the ratio of fat to muscle. Exercise every day, eat regularly, go to bed early and get up early, and if possible, it is best to sleep before 10 at night (good for the skin). Finally, I wish you success in gaining weight!