Hi, You should gain weight not by increasing fat in your body but by increasing the metabolic rate and the muscle mass. You should focus simultaneously on food and exercise. Food should be nutritious and not fatty. The medicines should be according to your digestive capacity, hunger, sleep, state of overall health, diseases, body constitution and medical history. Initially you should follow body detoxification for first 7 days Please find a general detoxification treatment Dashmooladi kwath 10 ml early morning empty stomach. Avoid food for 30 mins after taking medicine. Hinguashtaka churna 1 tsp before every meal Triphala 1 tsp with warm water before bed at night. Hope this helps!