From an evolutionary standpoint, people able to put on fat were better able to survive periodic famines and other hardship.
Especially in cold arid polar region.
People crave fats and sugar for the reason you described. It is just that those substances are too abundant these days. They ended up as health hazard now. However, this would be the first time in history.
When food becomes scarce again, waif looks will disappear in an instant and curvy traditional beauty looks will be in.
One thing is for certain. At any age, to be qualified as a beauty is extremely hard. When food is abundant, one should be extremely thin. When it is scarce, one has to be curvy and even plump. Go to any traditional societies and show them the pictures of Marilyn Monroe and Kate Moss. In all likelihood, the former will get near-universal approval while the latter will get unanimous thumbs down.