You can’t tell your body where to deposit weight, but if you build muscle, your weight will be more evenly distributed, and, if you don’t, fat will settle in your abdomen. Some people have a body type that resists gaining muscle and fat. They should build muscle through weight-training while limiting aerobic exercise to 30-minutes per day. You should also keep track of your bloating because it could signal a medical condition that leads to a loss of nutrients. To gain weight, eat a balanced diet with 250 to 500 calories above your maintenance needs.