Humans need calories, it's true, but more than that we need nutrients. McDonald's food is carefully processed and stripped of its natural nutrients, so that you

Humans need calories, it's true, but more than that we need nutrients. McDonald's food is carefully processed and stripped of its natural nutrients, so that you need to eat much more of it to get the nutrients you need. It's also packed full of calories, so that it tastes good, so eating enough of it not to be malnourished requires eating a lot of calories as well. I rarely see grad students eating at McDonald's.