A new study out of Yale University tells us that the brain sees the combination of carbs and fats as more rewarding than either of these nutrients taken separately. People are more willing to pay more money for foods that combine the two, for instance, potato chips, than for foods representing only one or the other of these food groups. The brain lights up in different areas for these two foods.
That means that grains light up one portion of the brain, while butter lights up another. So if you eat them together, double the reward! When we see foods combining the two groups, our brains make the connection and prompt us to be willing to pay more money to buy these foods. Which of course leads to obesity.