An appetite for food addiction?
Many of us enjoy foods that are high in sugar, fat, salt, or a combination of the three; take savoury biscuits for example. Dr. David Kessler’s The End of Overeating explores in detail the art and science behind the creation of highly palatable foods. Despite their appeal, most of us are able to exhibit adequate control when consuming or over consuming these foods. However, there is a subset of the population for whom control over these foods becomes problematic and can result in unhealthy weight gain or obesity. For these individuals, consumption can become life threatening. Why is it that some who wish to reduce their intake of these foods are not able to do so?
While some may point to weak willpower or misplaced motivation, prominent neuroscientists have suggested that the failure to regulate eating behaviours is symptomatic of a food addiction. Dr. Nora Volkow, the effervescent director of the National Institute on Drug Abuse and one of the most vocal advocates of the brain disease model of addiction, has argued that some forms of obesity should be included as a mental disorder in the latest iteration of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). The case for food addiction is based on several lines of evidence. Animal and human neuroimaging studies have shown that some foods, particularly those high in sugar, fat and/or salt, can produce changes in the brain similar to those produced by addictive drugs, such as cocaine and heroin. This is unsurprising given that drugs of addiction were originally shown to act on the neural pathways that mediated everyday rewarding activities, such as eating (see here for a thoughtful exposition). There also appears to be a common genetic risk for vulnerability to drug addiction and obesity. Patterns of eating in obese individuals, in particular those with binge eating disorder, also closely resemble key behaviours exhibited by drug abusers.
Leaving aside concerns regarding the strength of the evidence presented in favour of food addiction and an addiction model of obesity (see Ziauddeen et al. and Epstein et al. for informative reviews), what would be the social and clinical implications of labelling overeating and certain subsets of obesity as an addiction?
It has been argued that food addiction could improve our understanding of obesity and the development of more effective treatments and policy measures to reduce over consumption. Its effect on stigma is less certain. Obese individuals may come to view their weight and eating as something outside of their control; they are not just suffering from urges that encourage weight gain but are suffering from a ‘brain disease’ that causes them to overeat. Research is needed to understand what implications an addiction model of obesity will have upon individuals struggling to reduce their weight and to control their eating.
Dr. Robert Lustig and colleagues, among others, have argued that neuroscientific research on the addictive properties of certain foods provides compelling evidence for policies that reduce their consumption across the population, such as taxes and regulations on the sale and promotion of sugar. There is already strong epidemiological evidence for the efficacy of population-based policies, as well as practical evidence from those used to regulate tobacco. Neuroscience may in fact be used to promote a high-risk approach focussing primarily on individuals with or at risk of food addiction. This would be counterproductive as excess weight is a global public health concern whereby a shift away from processed energy-dense foods to those that promote health would be beneficial to most, not simply those deemed to be suffering from a food addiction. Historical behaviour of the alcohol, tobacco and gambling industries suggests that the food industry is likely to exploit this view. Our research (forthcoming) suggests that the public, while supporting the view that certain foods can be addictive, does not support commonly advocated population-based policies, such as advertising restrictions and food taxes, to improve levels of obesity. The reasons behind this warrant further investigation.
While the current enthusiasm of research into animal and human neuroimaging studies on overeating warrants thoughtful consideration, scientists and researchers should also consider the potential social and policy implications of their findings. The clinical impact of food addiction diagnoses on the ability to reduce overeating and weight also needs to be examined further. Contrary to popular accounts, an addition model of obesity may actually reduce obese individuals’ ability to control their eating and weight.