Hello Thanks for asking us. -Before I tell you how to become fat, I would like to suggest if I were your treating doctor, you should do a complete blood count (cbc) test. -How is the body composition of your parents , your brothers and sisters? To become fat- You should eat fruits like mango and banana more. you should eat more carbohydrates like chapatti and rice. And put ghee on chapattis and in morning eat paranthas. If you are a non vegetarian ,you should eat meat 150 gm daily. And one egg daily with yolk. Beside consuming milk with protein powder ,have a regular exercise and sleep for at least 8 hours. Sleep pattern must be undisturbed and should be of sound deep sleep. This will help you gain weight. Hope this answers your question. If you have additional questions then please do not hesitate in writing to us. Wishing your good health Regards