The Politics of the Science Behind Food Addiction

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.

There are a few things to note. One is that the authors do not know whether these brain dysfunctions ("the deficits in reward processing") are a result of overeating, a result of the type of food itself, whether some unknown factor causes this type of response, or whether the brain is pre-wired ("constitutive ") to respond this way to any type of overconsumption. Also, the media has already up-regulated the story. When the press writes that something "may" be like something else, people tend to believe that the two are linked, and that a common mechanism is responsible for both things. We assume this because we assume that the media is telling us something new and relevant. This is unfortunate; we need be very careful in how we consume scientific studies, lest our brains become inured to the scientific method, which is provisional and careful and always open to revision.  Headlines like "Fatty Foods May Be Just As Addictive As Cocaine and Heroin"  or "Twinkies As Addictive As Crack Or Smoke" are misleading. Slightly better is the National Institute of Health's own description: "Research suggests food availability could prompt addiction," which is at least faithful to the science, although not quite to what the authors found. (The headline implies causation; the authors find correlation.)

At the same time, strong correlations are often as good as scientists are going to get, and a series of strong correlations between mechanisms, repeatedly and regularly tested over time, and with other factors being ruled out one by one, come close enough to causation that a reasonable person  -- let's say a policy-maker -- can conclude that certain interventions might be necessary.  And there is a mountain of evidence that the food we eat, whether it's trashy empty junk food or sizzling, perfectly cooked steak, is specifically engineered for our pleasure. We wouldn't really have it any other way, and it's hard to blame the food industry for trying to make their food taste better.  The same foods that are addicting or addictive are also not, when consumed in reasonable quantities.

At the same time, given how quickly obesity sets in among young kids who begin to consume high sugar, high-fat, high-salt diets, you've got to wonder where else can one can allocate blame?  What is the "bliss point," as Kessler calls it, where food transits the boundary between enjoyable and addictive? Do food companies deliberately manipulate this point in order to draw in consumers who are bombarded by advertisements, who live in an environment where access to good food is spare and access to junk food is plentiful, and who lack adequate parental supervision to compensate?

The Center for Consumer Freedom, which is run by lobbyist Rick Berman and which gets paid by some food manufacturers, put out the only response I've seen yet from the industry, and it is weak: "Common use of the term 'addiction' has changed from describing a physical dependence on a substance (like hard drugs), to a psychological dependence."

Yeah. And the article discusses a physical addiction.

Thumbnail photo credit: Jennie Faber/Flickr