In his book, "The End of Overeating," former FDA commissioner David Kessler charges food companies with deliberately manipulating the chemical composition of their products to make them addictive to people with vulnerable brain chemistries— i.e., children. Kessler participated in subsequent research that found similarities in how rat's brains experienced withdrawal symptoms similar to drug withdrawal then, after being fed by a high fat, high sugar mix, they were suddenly put on a diet. The food industry dismissed Kessler's claims by ignoring them, and one of their top lobbyists admitted that the strategy was deliberate: to respond would call attention to the claims and force the good companies into a tit-for-tat debate about neuroscience. Kessler believes that many food companies ought to be publicly shamed for constructing and marketing addictive, unhealthy food to kids.
More ammunition comes today in a new article from Nature Neuroscience, which found that rat brains tend to crave higher and higher levels of fat and sugar over time in order to make the reward centers send out the "satiety!" signal. The article provides evidence for a conclusion that many overeaters intuit: food can be addictive. More precisely, in rats, certain types of food can mimic the mechanism by which the rats (poor rats!) also become addicted to drugs. The authors conclude that the "development of obesity was coupled with emergence of a progressively worsening deficit in neural reward responses." Specifically, a specific type of Dopaminergic neuroreceptor called the D2 Striatal appears to be "downregulated" in rats who become obese. The same receptors show down-regulation in humans who have become addicted to drugs. (It is very difficult, incidentally, to study in vivo changes to human chemical receptors, which is why analog studies conducted on rats are still the norm." In humans, the compulsion to overeat could be chemically tied to a brain region (the dorsal striatum) that, over time, is harder and harder to trigger. It turns out that the dorsal striatum is implicated in what scientists like to call the "hedonic" response—the feeling of pleasure and fulfillment one gets for performing a certain activity.