The latest fad in obesity research is to claim that Americans are fat because “fatty food [is] addictive as cocaine,” to borrow from a Bloomberg News headline. Needless to say, Kelly “Twinkie Tax” Brownell is pleased by the implications of these claims, as they could “change the legal landscape.” Note well his choice of adjective.
But how much scientific weight do claims that you can “maybe” get addicted to ice cream hold? According to three Cambridge University researchers, they don’t hold the weight Brownell hopes they do. Reviewing existing literature in an editorial in Nature Reviews Neuroscience, the researchers find “several fundamental shortcomings in the [food addiction] model.”
Among the problems with the “addiction” hypothesis noted in the article — and ignored by scary news stories — is the inconsistency of the results. (“Cookies aren’t cigarettes, just like we thought” just doesn’t have the same ring to it as “Ice Cream: A New Heroin?”.) With drug addiction, the results of brain imaging studies are clear and consistent, suggesting an addiction process. With obese people, they aren’t. Additionally, the Cambridge reviewers found no consistent evidence of withdrawal symptoms from food. To put it more generally, clinical “criteria for substance dependence translate poorly to food-related behaviours.”
The reviewers end their article with a warning, advising researchers against hastily adopting an addiction model in light of conflicting evidence. They argue that holding to a broad, Twinkies-are-crack model of food dependence in spite of the evidence will lead to “misguided” policy recommendations. “The vast majority of overweight individuals have not shown a convincing behavioural or neurobiological profile that resembles addiction,” they conclude, dealing a major blow to the theories of folks like David Kessler.
The last time “food addiction” hit the headlines, lawyers used it to threaten food companies with lawsuits. Now, Kelly Brownell sees “food addiction” as a legal game-changer. Unfortunately for him and the John Banzhafs of the world, this personal-responsibility poison pill doesn’t seem to be a scientific game-changer.