Anorexia nervosa is commonly attributed to psychological conflicts, attempts to be fashionably slender, neuroendocrine dysfunction, or some combination of these factors. Considerable research reveals these theories to be incomplete. This article presents evidence that anorexia nervosa's distinctive symptoms of restricting food, denial of starvation, and hyperactivity are likely to be evolved adaptive mechanisms that facilitated ancestral nomadic foragers leaving depleted environments; genetically susceptible individuals who lose too much weight may trigger these archaic adaptations. This hypothesis accounts for the occurrence of anorexic-like syndromes in both humans and animals and is consistent with changes observed in the physiology, cognitions, and behavior of patients with anorexia nervosa.
Why has the evolutionary perspective of Anorexia Nervosa been overlooked? Researchers may dismiss adaptationist arguments as untestable, but reasonable conclusions can be reached by weighing evidence and judging probabilities. Psychosocial explanations explain little biological data and are undermined by observations that symptoms are similar across era, sex, and culture, as well as by twin studies showing little influence of family environment.
Cognitive behavioral therapy, dialectical behavior therapy, compassion focused therapy, acceptance and commitment therapy - all helpful in treating anorexia nervosa. However, let’s fine-tune these approaches with what we are learning about how anorexia nervosa actually works.
Cognitive behavioral therapy for eating disorders focuses on the wrong underlying cognitions. An underweight person with anorexia does not run and restrict because she is vain, but because of neuroendocrine changes that have evolved over time. Let's refine the culture-bound explanation of anorexia that has dominated our culture. Anorexia is not simply "fear of being fat."
Anorexia outside of the environment in which it evolved can be deadly. Starving rats and mice will run themselves to death in a lab cage, but in the wild their anorexic behaviors would have brought them to a better foraging area, where they would have survived and thrived. Anorexia evolved in the context of deeply social bands and it is probable that the whole tribe helped their anorexic scout recover.
Explanations attributing anorexia to biological dysfunction lack explanatory coherence. In contrast, an evolutionary explanation does account for the broad array of anorexia phenomena, and it is supported by extensive evidence from multiple independent sources. Evidence strongly suggests that symptoms of anorexia are an evolved response to starvation.
The Adapted-to-Flee-Famine Hypothesis has proposed that abilities to ignore hunger, deny starvation, and move energetically are remnants of archaic adaptations that helped some in starving hunter-gatherer bands lead others from depleted home range. Eight genes have been identified in individuals with anorexia that decrease appetite and increase activity, triggered by falling weight.