Define Energy requirements for Underweight?

The total calorie intake should be 500 to 1000 Kcal in excess of the daily needs in order to result a gain in weight by half to one kilogram in a week. Thus, if you need 2000 Kcal for your normal activity, you require 2500-3000 Kcal per day for weight gain. We can also compute the energy requirements on the basis of ideal body weight. The patient may be given 30-35 Kcal per Kg ideal body weight per day. The calories should be increased gradually over a period of one or two weeks to avoid digestive disturbances.