People with Prader-Willi syndrome want to eat constantly because they never feel full(hyperphagia), and they usually have trouble controlling their weight.
If children are allowed to eat as much as they want, they'll quickly become dangerously overweight. A child with the syndrome can eat 3 to 6 times more than other children of the same age and still feel hungry.
Limiting food intake can be very challenging for families. Children may behave badly to get extra food, and their hunger can make them hide or steal food.