Hi Rahul, You say you are 156 cms and your weight is 58kg and you want to gain weight.First of all you are not underweight but as per national guidelines, of normal body weight for your height (56-60kg). I think you should stop worrying about gaining weight and cocentrate instead on gaining health. You can do this with regular moderate exercise--an hour of gym, walking, jogging, games, yoga; and a nutritious healthy diet of whole cereals, fruits, pulses, legumes, vegetables and dairy products with less of refined products, fried and oily, salted snacks and sweets.