According to bmi-calculator.net, if your body mass index is less than 18.5, you are underweight. Being underweight can be just as problematic as being obese. When a person is underweight, he risks supression of the body's immune system. Once the immune system has weakened, a myriad of other health problems begin to arise. A well-balanced diet is the best way to increase weight and remain healthy at the same time.
Increase your calorie intake. Begin to eat foods that are replete with carbohydrates, including whole grains, pasta, beans, rice and oatmeal. Avoid eating fattening foods and oil. Cook with oils like flax and olive oil. Gaining weight does not mean you go on a eating rampage, consuming everything in sight. Eat foods with nutritional value. Make sure you get protein sources, such as lean meats, vegetables and fruits.
Plan to eat six to seven small meals a day. Aim to eat around 400 calories at each meal, or about 2,800 calories a day.
Develop a weightlifting workout regimen. Weightlifting is a good way to gain weight without adding fat. Try to lift at least twice a week. Get with a trainer at a local gym if you are not sure how to get started.
Consider taking a meal-replacement or weight-gain supplement. Get better results with your supplement mix by adding them to peanut butter and various fruits. Mix your meal-replacement powders with skimmed milk and juice instead of water.
Kick bad habits like smoking and drinking, which may reduce your appetite.