Last month I wrote about a media-friendly study that found behavioural and physiological similarities between drug addiction and junk food addiction in rats. Drug abuse experts David H Epstein and Yavin Shaham recently wrote a commentary on this study in the same issue of Nature Neuroscience that the study was published. They criticize misleading news headlines that suggested the study has pinpointed the cause of obesity.
In fact, food addiction is very different from obesity. The closest syndrome to food addiction accepted by the medical community is the psychiatric ‘binge-eating disorder,’ a condition that affects far fewer people than obesity does. Therefore food addiction cannot account for our obesity epidemic. At best, food addiction is a small factor among many others that contributes to obesity.
Epstein and Shaham make the following conclusion about summaries of the junk food study
We would be mistrustful of any summary simpler than this: given enough access to cheesecake and bacon, rats display patterns of eating that resemble those that account to some unknown degree for human obesity and these patterns seem behaviorally similar to, and share some neuro-physiological substrates with, patterns of drug self-administration and withdrawal symptoms that resemble those seen in drug addiction.
I re-read my post on the study in light of this skeptical view. Would I have won the commenters' trust?
Well, a good feature of my post is that I didn’t mention obesity. However, by talking about taxing soft drinks and the grossness of a McDonald’s Happy Meal, I may have implied that the results of the study can tell us something about obesity. Indeed the soft drink tax proposition is largely lobbied as part of the fight against obesity. I apologize to my readers if any connection between food addiction and obesity was implied.
Another error I made was failing to summarize the behavioural findings of the study and remaining agnostic as to whether quitting junk food can lead to withdrawal symptoms. As mentioned in Epstein and Shaham’s commentary, the behavioural findings indicate a resemblance to drug addiction, and there actually were signs of withdrawal in the junk food-fed rats. Food addiction is clearly more than just a low concentration of D2 receptors in the brain’s dorsal striatum. In fact Epstein and Shaham importantly note that low D2 expression is associated with cocaine addiction in ventral, not dorsal, striatum. So the behavioural findings are the parts of the study that are most relevant to drug addiction.
Now on to the next question: is television addictive too?