Heavier bulemics have an easier time staying in therapy.
File this in the "it makes sense now that I think about it" department ...
In an article titled, "Weight Suppression Is a Robust Predictor of Outcome in the Cognitive-Behavioral Treatment of Bulimia Nervosa" (Journal of Abnormal Psychology, February 2006 Vol. 115, No. 1, 62-67), Meghan Butryn, of Drexel University and other colleagues at Drexel and Stanford report on the characteristics that predict bulimic patients' ability to tolerate cognitive behavioral therapy for bulimia.
Bulimia, of course, is an eating disorder that occurs when people (usually women) enter into a repetitive cycle of binge eating and purging (vomiting up what has been eaten). Bulemia is distinct from Anorexia, the more well known eating disorder that occurs when people (usually women) starve themselves in the pursuit of ultimate thinness. Unlike skeletal anorexic people, bulimics are typically at normal weight when they appear for treatment. This normal weight is deceiving, however, becuase binge and purge cycling behavior typically starts as a weight loss strategy. Bulimic people typically start out overweight, and use their purging as a means of losing weight. Bulemics may engage in food restrictions for a time, but then usually end up losing control, binging, and then trying to gain it back through purging, exercise, or more food restriction. All that food restriction requires an enormous amount of energy to maintain. During their binge episodes, bulemic people lose their inhbitions towards desired food, and consume mass quantities of it. Most of the time, as the binge ends, they will attempt to shed all the calories they've eaten, usually by throwing it up, exercising, or going back on food restriction.
What the researchers found is that it is easier to treat bulemic people who have not successfully used bulemic behaviors to achieve "weight suppression". Weight suppression has occured when a bulemic's weight has dropped substantially from her maximum lifetime weight due to purging behaviors. Bulemic patients who lost a lot of weight before entering treatment tended to drop out of treatment with much greater frequency than bulemic patients who had not lost a lot of weight. In fact, they were able to quantify the likelihood that a given patient would drop out of treatment early, knowing only the difference between her highest weight and current weight. "On average, for each increase of 1 kg of weight suppression, the odds of not completing treatment are multiplied by a factor of 0.69." "Facinating", as Mr. Spock would have said.
Why should the amount of weight that bulemic people have lost determine their ability to tolerate treatment? The researchers educated guess is that these people are reacting with fear to the therapy's instruction to resume a normal eating pattern (charcterized by a wider variety of foods, small normal meals and snacks), and that this fear may have merit. Bulemic people who have lost substantial weight appear to be be very much like obese people, in that their metabolism has been tuned (by genetics, and by their very binging and purging activities) towards storage of calories rather than consumption of them. Instructions to eat a greater range of foods and to snack between meals (instructions intended to ward off hunger feelings and cravings) might actually lead to weight gain for people with storage-oriented metabolisms! If this is true, it would suggest that cognitive therapists need to modify their approach so as to better mange weight suppressed bulemic patients' very real fears of weight gain. There might be two non-mutually excusive ways of going about this: by designing a diet with a caloric intake matched to the patient's metabolic needs, and yet still containing more variety of foods and more frequent eating times, and by addressing fears of weight gain head on with cognitive techniques.