Physical Craving and Food Addiction
In 1993, Wilson reviewed the scientific research on binge eating and found the theory that foods cause physical cravings was “without convincing empirical support.” In l994, Nobel et al at UCLA discovered that some obese adults who were “bingeing on dense carbohydrates” and who were neither alcoholic nor drug addicted had the same D2 dopamine gene marker that distinguished alcoholism and other drug addictions. In the following years, Hoebel et al at Princeton reviewed 251 animal studies designed to mimic human ingestion of sugar and found positive indication of physical craving. More recently, Ahmed’s research in France showed that intense sweetness – not just refined sugar, but also artificial sweeteners – surpasses cocaine as a reward in laboratory animals. Just this year (2009), Leibowitz of Rockefeller University demonstrated that overconsumption of fats can be correlated with brain systems which, when activated, further stimulate the intake of fat. Gold at the University of Florida presented summaries of the brain imaging research at several leading universities showing that “palatable food” created the same types of changes in the dopamine receptors of the human brain as alcohol and other widely recognized addictive substances. And a series of studies by Wang of the Brookhaven Institute now demonstrates that those with severe problems with foods can be triggered simply by viewing pictures of the foods on which they tend most often to binge. At such times, their brains look like they are already experiencing a state of biochemical craving.
Colantuoni et al (2002) analyzed over a hundred peer reviewed articles, each of which showed that humans produce opioids – the chemically active ingredient in heroin, cocaine and other narcotics – as a derivative of the digestion of excess sugars and fats. Ifland et al (2009) established that some obese adults were able, while overeating refined foods, to identify a physical craving for these foods as a significant and frequent trigger of bingeing behavior. Drewnowski at the University of Washington, Bellingham has reported an experiment showing that naloxone, a common opiate blocker, curtailed people’s interest in candies, cookies and other sweets when compared with those who did not take this drug. Noble’s genetic research, Gold’s brain imaging research, and the research on endogenous opioids – including opioid blockers inhibiting craving of foods – all focus on pleasure enhancing aspects of physical craving and converge at the D2 dopamine receptors, that is, the pleasure centers of the brain.
There is also research on out of control consumption of food related to the pain reduction centers which focus on the serotonin mechanisms in the brain. Katherine summarized the research showing malfunctions in serotonin processing correlates with an addiction to sugars and flours.
There are studies suggesting other biochemical explanations for aspects of out of control eating. Shapira et al shows that behaviors of people with low leptin levels, especially those with Prader-Willi Syndrome, tend to be related to the behavior of those with very strong biochemical urges to eat and binge on all foods – what self-assessed food addicts call “volume addiction” or “overeating of all foods.” Those with celiac disease – an allergy to gluten, especially wheat – experience insatiation for completely different biochemical reasons. Similarly, Gonzales, from her clinical work with food addicts as a dietician, developed a theory of how deficiencies in the insulin system could create a “false starving” experience in self-assessed food addicts.
Findings from laboratory-based scientific research correspond closely with other clinical observations of professionals working with food addicts. Working with 4000 food addicts over twenty years, Werdell found that bingeing clients reported “having to eat” and “bingeing on” the same foods scientists find most “addictive”: sugar, fat, flour, wheat, salt, artificial sweeteners, caffeine and volume. Kriz’s research found that self-assessed food addicts in Overeaters Anonymous were successful in weight loss by dealing first with physical craving and abstaining completely from their major binge foods. Carroll studied five year outcomes of a selected sample of 8000 alumnae from a psychiatric hospital’s residential food addiction program – for those whom dieting, therapy and even 12 Step programs had not worked – and found they were treated at least as successfully in an “addictive model” program as alcoholics and drug addicts were treated in residential chemical dependency programs. That food abstinence relieves physical craving, enables sustained weight loss and supports internal recovery, provides a strong argument for the existence of both physical craving and food addiction.
There is substantial evidence that some binge-eaters experience physical craving, that is, craving that can be characterized as being primarily physiologically-based rather than psychologically, socially or environmentally-based. This does not mean that social and environmental factors do not contribute to most of these situations. Fairbank’s and Wilson’s 1993 data make it clear that prior trauma, family dysfunction, and lack of rational-behavioral skills are correlated to binge eating disorder, and Adam and Epel’s recent review of current scientific literature assures us that stress – and the inability to cope with stress without food – continues to be an important cause of eating disorders and obesity. However, for those whose problems with binge eating are progressive and cannot be successfully treated with dieting, behavior modification or talk therapy, there is often an internal chemical basis to the problem. There is now more scientific verification for physical craving as a part of food addiction than there was for physical craving with regard to alcoholism and other drug addictions when they were first designated as substance use disorders. There are important implications for treatment and for related public health policy.