Hi.... Only calories won’t add to your body weight,include the right amount of proteins to your diet. Remember , if you want to put on weight and look fit, you need to build muscles not flab. Eat - Eggs, lean meat, fish, pulses, sprouts, and dairy products that rich sources of proteins. Fish such as tuna and mackerel are rich in oil and are one of the best ways to increase weight..... Take care with dairy products. If you're lactose intolerant, try substituting yogurt for milk. Or use an enzyme product to help break down lactose. Consuming small amounts of milk products or combining them with other foods also may help.