Supermarket Effect
The variety of food types and flavors encourages overeating. The brain is always interested in something new or changing. Eating the same food or flavor, we quickly become full and bored with eating. But at a Thanksgiving dinner or a buffet or banquet, it is easy to find stimulation for renewed eating.
An excerpt from Neurogastronomy: How the Brain Creates Flavor and Why It Matters, by Gordon Shepherd.
There are several theories for why we overeat.
One theory is based on the observation that even though a rat may have fed to satiety, it can be induced by conditioned cues to keep eating. [Dana] Small and her colleagues mention an experiment that demonstrates this. In this experiment, rats learn to associate the presentation of food with the sound of a buzzer, much like Ivan Pavlov’s dogs. If the buzzer sounds when they are sated, they will begin to eat again.
Instead of buzzers, humans have many other cues that keep them eating flavorful foods. In our example, a burger cues a bag of potato chips, then the ketchup, then the soft drink, then the . . . This kind of feeding has been shown to be dependent on connections between the amygdala, a node in the emotional network, and the hypothalamus, which is involved in activating feeding. These connections become hypersensitive because of long- standing habits.
Another idea is that overeating is due to ineffective inhibitory circuits in the prefrontal brain regions, combined with heightened excitability of the circuits mediating reward from the foods consumed. An analogy is the involvement of these circuits in drug cravings. This is more evidence that a tendency to overeat involves circuits at the highest cognitive, as well as emotional, levels.
Another factor is the possibility that overeating occurs because eating itself does not have adequate reward value; the brain does not register enough “pleasure” with lesser amounts of food.
In his book The End of Overeating: Taking Control of the Insatiable American Appetite, David Kessler, my former dean at the Yale School of Medicine, has emphasized the combination of salt, sugar, and fat as the main flavor villains to be resisted and controlled. Neurogastronomy supports this conclusion, identifying retronasal smell and its associated multisensory brain mechanisms of flavor as underappreciated major factors.
If flavor plays this central role in what we eat, the brain must contain mechanisms for making decisions about whether a food that produces an attractive internal flavor image in the brain is also nutritious. This is a final critical part of the human brain flavor system for determining normal function in healthy people and abnormal function in people who overeat.