Weight gain needs a healthy wholesome diet with inrease in proteins, healthy fats and required carbohydrate intake. Include more of fish, eggs, chicken, nuts and oilseeds in your diet with ample quantity of fresh fruits and vegetables. Do not skip meals and eat frequently. Do some exercise along so that digestion is good. Take care that you do not have constipation and are properly hydrated. If you need me to help you out with customized online diet chart, please contact us for a direct consultation through Lybrate or write to me.