weight gain program requires sustained efforts and holistic approach. Just eating more ghee or butter laden foods, or popping pills is not going to help you.  some tips are: 1. Rule out digestion issues like bloating, frequent indigestion, worm infestation, IBS etc. 2. Take smaller portions of, energy dense foods and  have frequent meals. 3. Don't drag over lunch or dinner more than 15-20 min. Chew food properly. 4. Drink water in between meals. 5. Do some light strength training exercise like dumb bells, push ups, Pilates etc. 6. Try to take balanced diet with fruits, veggies, nuts, sprouts, paneer, curd, whole cereals. Cut down on junk  food and outside food.  Preferably eat home-cooked food.