Have you ever wondered why people reach for food, any food, when they are under stress? With most people, this stress reaction is mild and episodic. But in others, it is extreme and frequent; they can consume 6, 7, 8 thousand calories in a single day. This syndrome of binge eating has attracted much attention among psychologists for a long time; and now neurobiologists have taken notice as well.
What’s going on?
I remember from my marathon racing days that at about 18-20 miles, I would hit a psychological low. I would be dragging my feet, having lost my motivation to make a new personal best, struggling with my rationalizations that I should just quit, even vowing to myself to never again engage in this idiotic effort. But then, I would pop something sweet (called Goo) into my mouth, and literally, within a minute or two, I would undergo a radical change: full of energy, motivated to pick up the pace, almost euphoric—I would sprint to the finish line. What an exhilarating experience! I didn’t waste any time registering for the next event.
Was it the extra shot of energy that caused the turnaround? Although this is the belief among runners, it couldn’t even begin to account for it. First, such an immediate effect could not be explained by an increase in calories; sugar takes longer to get absorbed through the gut (and Goo is formulated for slow release). Second, the amount of calories could not sustain a runner for more than a mile or two; the mood-elevating effect lasted for many more miles.
In a recent issue of Scientific American Mind, Prof. Michael Macht of the University of Wuerzburg, Germany, examines this question. He cites the classic research by Jacob Steiner of the Hebrew University of Jerusalem, which showed that a liking for sweet tastes is innate. When Steiner gave newborns a sugar solution, the babies made sucking movements, licked their lips, and relaxed their faces, looking satisfied. When given a bitter substance, the babies reacted with disgust, scrunching their eyebrows together and sticking out their tongues. Psychologist Elliott Blass of U. of Mass. Amherst found that a pacifier dipped in sugar solution lessened the pain of circumcision far more than an unsweetened one. The pain suppression occurred quickly, with a maximum effect achieved in 2 minutes. (My parents did even better. They dabbed sweet wine on my lips; my screams of protest turned into an angelic smile.) Whatever the case may be, the time frame of two minutes is suggestive of a brain mechanism, rather than a digestive one.
Pathways of addiction
Princeton University Professor Bartley Hoebel and his coworkers made rats sugar-dependent using a regime common to addicting rats to alcohol, heroin, nicotine, and other addictive substances. They repeated for one to four weeks a schedule of fasting and intermittent sugar availability. The rats gradually tripled their sugar intake and learned to binge on the sugar as soon as it was offered to them. In the sugar-addled brains of these rats, they detected a sharp increase in the neurotransmitter dopamine, specifically in the reward system. This is exactly the response shown by animals and humans addicted to drugs. What caused this rise was not related to digestion of the sugar—it was present even when the investigators removed the sugar from the stomachs of the rats using an implanted fistula. Most likely, the rise in dopamine was related to the sweet taste of the sugar.
How can binge eating be controlled?
Certain drugs inhibit craving in addicts. For instance, the drug Naloxone is widely used in counteracting intoxication with morphine-based drugs. Interestingly, Naloxone also causes suppression of appetite. I am not familiar with any drug trial that is aimed to specifically suppress binge eating. But who needs drugs? This is like fighting fire with fire.
Stanford psychologist Christy Telch and her colleagues experimented with 44 women with binge-eating disorder. Some received no treatment (the control group), whereas others underwent so-called dialectical-behavior therapy or DBT. In this Marxist-sounding therapy, the subjects learned to deal with negative emotions in ways other than eating. Over 20 sessions, a therapist explained the genesis and role of emotions and taught the women strategies for coping with stress, among other tactics.
The results? By the end of the experiment, the women who had DBT were having many fewer eating attacks than the control subjects, and 89% of those treated had stopped binge eating. Six months later, 56% of the treated women were still abstinent.
Yet again, we are seeing the inextricably intimate connection between body, brain, and behavior. So I am off to the kitchen for a piece of superb Scharffenberger chocolate to celebrate this axis of bliss.