A person needs to eat foods that contain calories, such as plants that contain fats, meal replacement drinks, dried fruits and animal fats, among others, as noted by WebMD. However, a person should avoid stuffing himself or herself as it can lead to an increase in body fat.
Eating foods rich in calories should be done following the right nutrition guide. For example, animal fats should not be taken excessively as they contain saturated fats, which can elevate bad cholesterol. A person who is underweight should aim to increase their weight gradually. The amount of food one eats a day is also crucial. Ideally, three meals and several snacks can help one attain their desired weight.