The quality and quantity of foods you consume along with the duration and intensity of physical activity that you pursue are key determinants of how effectively and quickly you will reach your weight goals.

In your case, it is important to gain quality weight, in the form of muscle. Muscle is developed best on performing resistant training (lifting appropriate weights) at least twice a week. Alternatively, you could play a sport or swim once a week. Water provides an ideal amount of resistance required to enhance and tone muscles.

 In addition to the above, it would be help to include protein rich foods in your diet from dals (pulses), legumes, beans, sprouts, to reduced fat milk, curds and cheese or paneer.
 Try and partner the above protein sources with wholegrain foods (wholegrain chapathi, roti and brown rice) and snack on fruits (good source of vitamins, minerals and fibre).
 Avoid high fat foods as much as possible  (e.g. chips, poories, sev, chivda) and opt for leaner baked substitutes.

 It’s preferable to buy fewer processed foods. When opting for a packaged product, always read the food label to know exactly what you are buying and compare the 100g columns of similar products.