Wednesday, June 17, 2009
Photo by Marina Komolova
One topic that never fails to generate a lively discussion is the relationship between obesity and personal responsibility. For example, in response to a post on psychological exams for bariatric surgery patients, one anonymous reader commented that:
I don't have a gym membership. I'm not even all that active. I live in a bad neighbourhood and i'm floating right around the Canadian poverty line. I'm not obese. When I see a little extra belly building over the winter, I watch how much I eat and try to expend a few extra calories in the comfort of the tiny living room. By blaming any other extraneous factors other than caloric-imbalance, we take away the inherent power from individuals to take charge of their own weight.
While it is convenient to villify obese individuals for their perceived lack of self-control, the evidence suggests that the situation is not so simple. This topic is explored in depth in this week's special issue of the International Journal of Obesity (IJO) titled "Obesity in a Modern World: When Pleasure Meets Homeostasis".
In a review article in this supplemental issue of IJO, Dr A Dagher of McGill Univesity examines the parallels between drug abuse and food "addiction", and discusses the implications for the current obesity epidemic.The crux of the issue is this; appetite is controlled by two separate systems. The homeostatic system, which is related to energy needs, and the hedonic system, which is focused on palatability and perceived rewards. If you eat a sandwhich because you are hungry, that is the homeostatic system at work. If you eat a sandwhich because you had a craving for a Fluffernutter sandwhich, even though you weren't hungry, that's the hedonic system.
I'm not sure how I feel about food addiction as a disease just yet, (Dr Dagher seems to have reservations about the term as well), but I have to admit there are some interesting similarities between drug-abuse and chronic over-eating. Both appetite and drug cravings are triggered by reward-associated stimuli - think of smokers who crave a cigarette when they see others lighting up, or the incredible allure of frying bacon. Further, both food and all drugs of abuse affect the secretion of dopamine, and blockade of dopamine receptors abolishes the cravings for both. Finally, both drug abuse and chronic over-eating are more common in individuals with a heightened drive for reward, otherwise known as impulsivity. These individuals require more stimuli (be it food, drugs, or adrenaline) to achieve a given level of pleasure or reward. This last point, as well as possible links between obesity and Attention Deficit Hyperactivity Disorder, is examined in depth in an article by Dr C Davis from the University of Toronto in the same issue of IJO.
Whether or not food addiction is an actual disease seems beside the point to me. It seems clear that food intake is influenced by hedonic stimuli. We happen to live in an environment which is completely saturated with these same hedonic stimuli, which target us, and our children, on an almost continual basis. Think of the ubiquitous ads for McDonald's and Coca-Cola - these are exactly the types of hedonic stimuli which have been shown to increase food intake. So is it any surprise then that we have an obesity epidemic, as millions of people are constantly being tempted to eat more than they need to? This very quickly leads to questions of free will and free markets and other thorny issues, but it becomes quite clear that advertising that promotes food intake is not in our societal best interest. Should we ban food advertising just like we banned cigarette advertising? I won't go that far... yet. However, it's becoming increasingly clear that like drug abuse, obesity is not always as simple as sheer will power.
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1. Psychological exams for obesity surgery.
2. High fructose corn syrup is ruining everything.
3. Misguided ad campaigns.
Dagher, A. (2009). The neurobiology of appetite: hunger as addiction International Journal of Obesity, 33 DOI: 10.1038/ijo.2009.69
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