Chris Kresser: That’s a term that’s used in the obesity literature. There are two primary ways that the brain regulates food intake. One is a homeostatic system, and that is the adipostat, the body fat set point, which you may have heard me talk about before, where the brain has a set point of where it thinks body fat should be, which is similar to a temperature that you might set a thermostat to. When the body fat level goes above that set point, the brain will kick in several different mechanisms to attempt to lower body fat back to the set point. And if body fat drops below the set point, the opposite will happen. The brain will kick in various mechanisms to increase body fat.
That’s the homeostatic regulation of weight, but there’s another system that influences food intake, and that’s the hedonic system, and that is governed by the palatability and reward value of food. For example, if you have two plates in front of you and on one plate is a plain steamed or baked white potato with no butter or salt, and on the other plate is a bag of potato chips, it’s pretty obvious to most people, without knowing anything about the science, that it’s going to be a lot easier to overeat the potato chips. Most people will only eat the plain white potato if they’re hungry, but many people will eat the potato chips even if they’re not hungry, just because they’re so rewarding and palatable.
The evolutionary reasoning behind the hedonic system is that foods that are rewarding and palatable tend to be energy dense, so craving those foods would have been protective. From an evolutionary perspective, it would have helped our ancestors survive because they lived in an environment of food scarcity, not food abundance like we live in now. And those very same hedonic systems that were protective in that environment of food scarcity are harmful in an environment of food abundance. In a nutshell, I think, that’s part of what explains the obesity epidemic.