Exercise very often plays a role in the development of restrictive eating disorders, particularly Anorexia Nervosa (AN). Some people view exercise as “a form of purging” or “a way to get rid of calories.” These explanations seem to make sense in light of modern western society’s views on exercise, similar to the theory that people with AN restrict their calories in order to conform to society’s thin ideal. But like the thin ideal theory, the “exercise purging” theory is an erroneous attempt to make sense of a puzzling symptom in the context of modern society.
In AN, excessive exercise, just like food restriction, is a biologically-based symptom, driven by something beyond conscious control or awareness. Patients do not exercise “to burn calories,” although they may insist that burning calories is their motivation. Consider, for example, the fact that even patients who know they are too thin are motivated to gain weight (yes, such patients do exist), often cannot stop themselves from moving unless they are forced to do so. Young children with AN are especially susceptible to the drive to exercise even though they have no idea what calories are or how to burn them.
A little history may help to put this into context. People did not really exercise for the purposes of physical fitness and attractiveness prior to the “exercise boom” of the 1970’s and 1980’s. However, hyperactivity was a symptom of AN long before Jane Fonda’s exercise videos found their way into American living rooms.
The nineteenth-century British Physician William Gull, the first clinician to describe AN medically, was surprised by the seemingly boundless energy that his anorexic patients possessed despite their emaciated state. In his 1874 paper entitled Anorexia Nerovsa, he wrote the following description of a young anorexic girl: “The patient complained of no pain, but was restless and active…it seemed hardly possible that a body so wasted could undergo the exercise which seemed agreeable.” Clearly, this young woman was not motivated by the pursuit of a thinner body, as the idea of exercising to “burn calories” would not emerge until a century later.
Animal research has shown that the hyperactivity commonly associated with AN is rooted in neurobiology and may serve an adaptive evolutionary purpose. For example, activity-based anorexia can be experimentally induced in rats which, like humans, evolved as opportunistic omnivorous foragers. When food-deprived lab rats are given free access to a running wheel, they become hyperactive, lose large amounts of weight, and will often die unless they are removed from these experimental conditions. I highly doubt that these rats were running excessively to purge calories, ward off obesity, or pursue some unrealistic standard of rodent beauty.
So why would AN, which leads to numerous health problems, infertility, and death, remain in our gene pool for tens of thousands of years? Shan Gusinger, an evolutionary biologist and a psychologist, posits that AN has evolved in humans as a means of helping us flee from food-depleted environments. The restless energy, grandiosity, and lack of awareness of one’s starved body allowed prehistoric anorexics to lead their tribes in migrations from food-depleted areas to plentiful ones.
Once the anorexic leader and her tribe arrived in a plentiful environment, the tribe feasted, pressuring the anorexic leader to indulge in food with them. In the absence of modern society’s thin ideal and without our modern obesity hysteria, prehistoric anorexics may have been able to allow their families to feed them, restoring their health and fertility. Even if the anorexic herself died of her condition or was rendered infertile, her close genetic relatives survived and reproduced, thus ensuring the continuity of AN into the next generation.
In our modern world, where children are encouraged to exercise more and make “healthy” (e.g. lower calorie) food choices as early as kindergarten, it is no wonder that AN is still around. During the pre-teen years, when rapid vertical growth and pubertal development demand extra energy, girls and boys are hit hard with the social pressures to be thin (for girls) or lean and ripped (for boys). The rapid weight gain that is necessary for growth and development is feared and despised in these growing children (and often, sadly, in their parents and pediatricians).
Adding add fuel to the fire, the pre-teen years are when intense and time-consuming athletic training begins. Competitive sports provide socially-applauded outlets for the young anorexic’s hyperactivity. No one bats an eye at the 12-year-old dancer who spends hours each evening at her studio in preparation for her next audition, or the 11-year-old boy who plays multiple back-to-back games each weekend with his elite travelling soccer team. Meanwhile, these children are making “healthy food choices,” consuming too few calories and fats to keep up with normal growth, let alone intense daily exercise.
In these vulnerable children, their vertical growth is stunted, their pubertal development is halted, and their intense athletic drive is praised by adults. And before you know it, they have fallen down the rabbit hole and developed full-blown AN. In this way, hyperactivity serves as both a precipitating factor and a perpetuating factor in the development of AN.
In my next post, I will discuss the role of exercise in eating disorder recovery.