You know, this website was not created for non answers! It was made to get answers not wicked remarks so I will go ahead and give one.
I am taking a guess here, the calories are determined depending on how much weight they need to gain. In some cases, they are started off slowly, 1000 calories a day. Ideally, a healthy person requires 1600-2000 per day.
In pride, the wicked holy pursue the afflicted;
Let them be caught in the plots which they have devised.
For the wicked boasts of his heart's desires, And the greedy man
curses and spurns the Lord