It makes sense evolutionarily: if there's lots of food available now, you should eat it, because there might not be enough in winter. We live in a society wher

It makes sense evolutionarily: if there's lots of food available now, you should eat it, because there might not be enough in winter. We live in a society where there's always lots of food available for most people in developed countries (who are mainly the people who are overweight), so it makes sense that you will instinctively eat more than you need to.