There are two divergent groups of brain imaging folks who believe dopamine [the “feel good” neurotransmitter] plays a role in disrupting the experience of hunger and appetite with those who restrict. Basically there are two theories on the table today.
The first suggests over eating types of eating disorders involve dopamine serving as the “reward” and “feel good” chemical released in the brain when overeating. However, with the restricting forms of eating disorders such as anorexia, the experience of increased dopamine concentrations when eating is unpleasant. Hence, the feelings associated with eating are negative for someone with anorexia and rewarding for someone with compulsive overeating or bulimia.
Another group of scientists are looking into the effects of fasting or restricting on dopamine levels for anorexics – the idea being a similar surge of “feel good” dopamine ensues – but this time stimulated by restricting to the point of starving. In other words, there may be a phenomenon for some people to “feel rewarded” by severely restricting their calorie intake. Accordingly, the more one restricts, at least in the early stages of anorexia, the more dopamine is released, the more rewarded they feel, and the more reinforced restricting behavior becomes. No one knows why some are prone to this end of the eating disorder spectrum as opposed to the other. In sum, this hypothesis suggests that dopamine “rushes” affect anorexics and overeaters alike, but for one group starving releases the chemical and for the other binge eating does the trick.
Here is an excerpt from Walter H. Kaye, M.D., one of the researchers at the University of California, San Diego who is looking into the above theories. His comments also touch upon a possible explanation for the body image distortions inherent with anorexia.
“The reason (anorexics) can go on a diet and lose all the weight is that their brain is not responding in a way that is driving eating.” Whether it’s not responding to the sensory aspect, it’s not the right signal about food, it’s not rewarding, we don’t really understand, but there’s something different about these homeostatic mechanisms.”
“The area of the brain known as the insula, is important for appetite regulation and also for something called interceptive awareness, which is the ability to perceive signals from the body like touch, pain, and hunger. It’s possible that some of the problems anorexics have regarding body image distortion can be related to alterations of interceptive awareness. There may be some dysregulation of insula function. This may in part explain why a recovering anorexic can draw a self-portrait of their body image that is typically 3X its actual size.” To quote from someone with this experience who is now recovering, “I was down to 80 pounds at five-foot six,” she says. “My self-portrait was so distorted I was able to lie down inside the drawing. But that’s how I saw myself.”
As someone who views eating disorders as part of the addictive disease continuum, I can’t help but wonder if this phenomenon also exists among alcoholics and drug addicts – namely some experiencing alcohol as pleasant yet most drugs as unpleasant and some having no preference for alcohol what-so-ever, but predisposed to experience certain drugs as impossible to put down.