Running Rats

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Activity-Based Anorexia in Rats. Animal studies have demonstrated that eating disorders can give rise to excessive exercise behavior, by inducing what is called “Activity-Based Anorexia” in rats. When researchers restrict rats’ food intake while giving them unlimited access to a wheel, the rats start running excessively. Paradoxically, these rats opt to continue running rather than eat during the short intervals of time food is made available to them. If allowed, they will literally run themselves to death.3 

Exercise in Anorexia Nervosa. Hyperactivity is a common, intriguing, and well-documented symptom of anorexia nervosa,4 noted as early as 1873 by the French physician Ernest-Charles Lasègue, one of the earliest writers about the disorder. Lasègue observed that patients with anorexia exhibited high levels of activity seemingly incompatible with their impoverished nutrition:

Another ascertained fact is, that so far from muscular power being diminished, this abstinence tends to increase the aptitude for movement. The patient feels more light and active, rides on horseback [the French text also mentions: ‘long walking-tours'], receives and pays visits, and is able to pursue a fatiguing life in the world without perceiving the lassitudes he would at other times have complained of. (Lasègue, 1873, p.266)

In one study, 37 percent to 54 percent of patients with anorexia nervosa (depending on subtype) engaged in excessive exercise. Patients may underreport the amount of time that they engage in physical activity, making it hard for caregivers and treatment professionals to fully assess.