Originally Answered: How to gain weight if you have a high metabolism?
First, add high calorie food items in your diet. To gain weight, you need to have more calories than burnt by the metabolic activities of your body. The amount of calories which should be taken daily differs from person to person. However, if you want to gain weight, intake of more calories will be beneficial. Second, add protein rich foods like fish, soybean, egg white, beans etc. in your diet.
Protein is a body building nutrient. It is very important to develop muscle mass. Third, consume more carbohydrates in your diet. It is very important for providing energy to the body. The carbohydrates which will not be used by your body will accumulate in your body as fat and it will also help you to gain weight. Fourth, add right kind of fats in your diet. Fat is very important to gain weight. Avoid those food items which have Trans and Saturated fats. Prepare your meals with canola oil, olive oil etc. which offers monounsaturated fats to your body.
Last but not the least, instead of having 2 or 3 meals in a day; take 5 to 6 small meals in a day. This will appease your hunger and will provide the source of energy to your body at different intervals in a day. Follow all the suggestions mentioned above, and get ready to gain weight.
Hope this helps :)