One more indulgence. A quote from A Room with a View
by E.M. Forster. For springtime.From her feet the ground sloped sharply into view, and violets ran down in rivulets and streams and cataracts, irrigating the hillside with blue, eddying round the tree stems, collecting into pools in the hollows, covering the grass with spots of azure foam. But never again were they in such profusion; this terrace was the well-head, the primal source whence beauty gushed out to water the earth.
Standing at its brink, like a swimmer who prepares, was the good man. But he was not the good man that she had expected, and he was alone.
The brain is named in beautiful words, intimidating words, but beautiful nonetheless. We'll start with the animal models of binge eating (1), which seem to have something in common with the human experience. Animals seem more likely to binge in cases of prior food restriction (and the bingeing can continue for long periods after restriction is over), and in periods of anxiety.
Daily binge eating on a "palatable sugar solution or fat diet" will repeatedly release the feel-good chemical dopamine from its home, the nucleus accumbens. Sugar-bingeing rats will have increased dopamine1 receptor binding in the nucleus accumbens, and decreased dopamine2 receptor binding in the dorsal striatum. This pattern is very similar to changes observed with drug dependency. There are also changes in opiate receptor expression in binge eating rats, and if you inject opiate into the nucleus accumbens, it will stimulate binge eating.
Some facts about binge eating in humans - the definition is that someone will eat an "objectively large amount of food" accompanied by feelings of loss of control. 30% of obese individuals attending weight control programs have the disorder. Obese binge eaters will eat significantly more calories than obese nonbinge eaters in order to feel full, or even when asked to eat normally.
In a study on humans, Wang et al discovered that food stimulus significantly increased dopamine signals in binge eaters in the basal areas of the brain, whereas non binge-eaters did not show the same increase.
Previous studies had shown that exposure to "palatable food stimuli" was associated with an increase in striatal dopamine release, and this release was correlated with ratings of "meal pleasantness" following consumption of favorite food. As with the other studies of folks with eating disorders, low dopamine levels (associated with an increase in receptors, to compensate) has been shown to be present in binge eaters.
People with binge eating disorder tend to overeat compulsively and have some impulsivity (also seen in substance abusers), and food is a potent reinforcer of the behavior, and fasting can enhance the rewarding effects (thus my little caveat about IFing and eating disorders).
Here's the evolutionary psychiatry money quote from the Wang article: "Some ingredients in palatable food such as sugar and corn oil can result in impulsive ingestion in patterns reminiscent of those seen with drug intake in addiction." DING DING DING DING.
And the sweet taste of sugar, without the nutritional component, can also induce release of dopamine (um� diet coke addiction, anyone?).
So I don't think I venture far out on a limb to suggest that eating disorders are addictive, or that certain types of extremely palatable food (sugar and corn oil, and in my clinical experience, for some people, wheat) are addictive. Abstinence with support is the tried and true method to help addictions. Hard, though, to get the appropriate sort of universal support when your government (and therefore any trained nutritionist or dietician or doctor of the conventional stamp) is telling you to eat corn oil and grains and carbs to lose weight and to be healthy in general.
Oh! Totally forgot to link yesterday in this blog - a new Psychology Today post is up. Click for me if you please!
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