In recent years, neuroscience has begun to solve the mystery of overeating. It turns out to have little to do with our taste buds, or even with our conscious desire for certain foods. Instead, the impulse to overeat depends on the pleasures of the stomach and intestines, which have an uncanny ability to detect the presence of calories. When we reach for that third helping of turkey, we are obeying the wishes of the gut, following a bodily desire that’s difficult to resist.