Hello there....., Everything we eat has some calorie content. So like we eat food with fewer calories to lose weight, we need to eat food that has more calories to gain weight.. Only calories won’t add to your body weight,include the right amount of proteins to your diet..... 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.....