The big players, calorically speaking, are fats and sugars. And the reason we desire them is because they activate our neural reward system, flooding those brain regions with the neurotransmitter dopamine. But studies show that fats and sugars trigger those rewarding bursts of dopamine in different ways. “This really got us thinking. Modern processed foods like French fries, donuts, hamburgers and even yogurts contain high levels of fat and carbohydrate. In contrast, foods high in fat and carbohydrate are very rare, if they ever existed at all, in the natural food environment. So we wondered, if fat and carbohydrate both release dopamine, might it be the case that their simultaneous consumption produces a super additive response, resulting in foods that are more reinforcing, calorie for calorie?” To find out, the researchers set up a sort of snack-attack auction. Participants were given some spending money, then shown pictures of familiar foods and invited to bid. The edible items fell into three categories: those high in fats but low in carbs, like cheeses; those packed with carbs but lacking fats, like pretzels; and those that were full of both, like cookies.