There is no denying the pleasure one gets from eating particular kinds of food. Chocolate, for example, is reputed to be an aphrodisiac, euphoriant, stimulant, relaxant and antidepressant, which is why it has been a popular component of food and drink for well over 1,000 years.
Yet, while some people may claim they are addicted to food (some jurisdictions favour this model and have even legislated that warnings akin to those found on cigarette packages be included on certain food labels) — there is a strong reluctance to classify food as an addictive substance.
The primary difference between obesity and addiction lies in the nature of the substance itself. Unlike alcohol, drugs, gambling, or gaming, food is essential for health and homeostasis.
“You cannot live without food. You can never drink [alcohol] again and that might be good for you. But you can never not eat again,” says Dr. Jacqueline Carter, a psychologist at Toronto General Hospital and Associate Professor at the University of Toronto. “For this reason, I do not classify obesity, and more specifically, binge- eating as an addiction.” (See below for more on binge-eating.)
This, however, does not dismiss the similarities between addiction and overeating or binge-eating. Dr. Alain Dagher, a neurologist at the Montreal Neurological Institute, has used functional magnetic resonance imaging (fMRI) to track how food, drugs, and other stimuli affect the reward centre in the brain. His recent research has focused specifically on obesity.
“It’s useful to look at obesity and related disorders, such as binge-eating disorder, through an addiction framework because it helps us understand the neuropathic mechanisms that cause people to overeat,” says Dr. Dagher. “The process which leads someone to become obese is very similar to the process that leads someone to become addicted.”
This parallel process is neurobiological in nature and can be divided into two primary mechanisms. The first involves the brain’s reward pathway. Substances such as alcohol and drugs act upon this pathway to generate a pleasurable response, but the response is also triggered by many foods, particularly those that are high in fat, sweet, or highly palatable.
“The body’s appetite circuitry — in which the reward centre is a pivotal part — developed during a time when people had to work hard to get their food,” Dr. Dagher explains. “People had to go out and catch it or harvest it; it wasn’t as readily available as it is today and generally the food quality was vastly different — lower in calories, sugar, salt, and fat. Hunger was a drive for survival. Now all we need to do is drive down the street to get food.”
There are many components that can work together or individually to stimulate the reward circuit. These include:
• Dopamine, a neurotransmitter, which is released by all abused drugs and by food; • Leptin, a hormone secreted by adipose tissue that functions as the primary appetite suppressant; • Ghrelin, a hormone secreted by the stomach that stimulates hunger; and • Insulin, a hormone that regulates energy and glucose metabolism.
The hormone ghrelin has been studied extensively for its correlation to the reward centre of the brain. One study of normal-weight individuals found that the introduction of ghrelin at the completion of a meal can trigger a desire for more food. “We can all relate to the experience of having a full stomach, yet still being tempted by a piece of cake, simply because of the reward your body perceives,” says Dr. Dagher. “It is this ability of food cues to trigger appetite that is a major part of the obesogenic environment — we are constantly bombarded by food images, aromas, and advertising.”
The second way in which alcohol or drug addiction parallels overeating and binge-eating is vulnerability: some people may be more vulnerable to highly rewarding foods.
“There are individual differences in people’s vulnerability to food,” says Dr. Carter, who is also a noted expert in eating disorders. “Research suggests that some people may have a genetic predisposition to get ‘addicted’ to certain types of foods simply because they find them more rewarding than somebody else. It’s similar to alcohol consumption — some people find it more rewarding than others and may therefore be at risk of developing a problem.”
Dr. Carter has been studying the genetic, psychological, and personality differences between people who binge eat and are obese and people who don’t. Her findings to date suggest that certain genetic factors are more common in obese individuals who overeat and binge eat than those who are lower in weight. It has also been documented that people with binge-eating disorder have a high co-morbidity of substance dependence, suggesting that food and other substance dependence may have the same genetic trigger.
What this trigger is and how it works, is not yet clear. One hypothesis is that the genes may affect a person’s ability to act on increases and decreases of ghrelin. However, obesity is not linked to medical imbalance of hormones, except in two rare conditions: congenital leptin deficiency, an early-onset disorder characterized by morbid obesity at a very young age, and Prader-Willi syndrome, a genetic disorder distinguished by high levels of ghrelin and excessive appetite that often leads to obesity.
Dr. Carter also rejects the disease comparison when treating patients with binge eating disorder. “Such classifications place obesity on par with addiction as something that cannot be controlled. Thus, the binge eater is powerless to control his or her actions and will always be a binge eater. But, as research shows us, these are biological and/or psychological drives and I think that people can make behavioural, psychological and emotional changes in order to manage their emotions and respond to cravings.”
Binge-eating is an episode in which a person eats an excessive amount of food in one sitting, often very rapidly. According to eating disorder specialist Dr. Jacqueline Carter, people with binge eating disorder generally overeat and, in addition, have episodes of binge-eating at least once per week. The disorder is not accompanied by extreme weight-control behaviours that are typical of other eating disorders such as anorexia nervosa or bulimia nervosa. As a result, people with binge-eating disorder often become obese, or at least overweight. Not all people who are obese have binge-eating disorder, but binge-eating disorder often leads to obesity.
Binge-eating disorder will be a newly recognized eating disorder in the updated edition of the Diagnostic and Statistical Manual of Mental Disorders, scheduled for release in 2013. Currently, only anorexia nervosa and bulimia nervosa are listed in the manual. Both are eating disorders that typically affect girls and young women. In contrast, the average age of people affected by binge-eating disorder is older — between 46 and 55, according to the US National Institutes of Health — although it can affect people of any age. In addition, both men and women are likely to have binge-eating disorder.
Questions for patients:
• Do you ever have episodes when you eat what most people would regard as an abnormally large amount of food?
• What would you typically eat at these times?
• Do you experience a sense of loss of control during these episodes?
Beating the binge:
• Patients with BED should seek psychological help. Cognitive behavioural psychotherapy (CBP) has been shown to be highly effective in dealing with this disorder.
• Eat only in one place in the house, such as the dining table. Do not eat in locations where there is a high probability or history of binge-eating (such as in front of the television).
• Eat slowly and mindfully. Focus on eating and do not couple eating with any other activities.
• Avoid trigger foods. Keep favourite binge foods out of the house, similar to what an alcoholic would do with alcohol.