The methods to gain weight are to eat more calories. The foods with the highest calories are fats and proteins. To stay health though, you can still gain weight and eat all the food groups. There are medications that will increase you appetite. For example, antidepressants. You can speak to your doctor if you feel depressed, because this can be a cause of low weight.
I hope this helps you!
Thanx 4de answer but im sorry i need only de medicine not de advice bcoz i did dat all so plz do back my deposit.never mind