It depends on the man. Some men prefer larger women over skinnier women because of all the curves, and usually bigger *assets*, haha.
Because they're fat.
Is a skinny man really skinny? You decide
No they arent
Twinkies, even better, deep fried twinkies. And if you're really desperate some drugstores sell nutrition bars that add weight onto your body. But I don't know why you'd want to be fat...
Why Men Are Getting Fatter Than Women