ble and diverse evidence reviewed here supports an evolutionary explanation for AN, the latest Diagnostic and Statistical Manual of Mental Disorders-5th Edition (DSM-5) maintains traditional psychosocial explanations for the disorder; this stance perpetuates a mistaken view of AN. Criteria include “persistent restriction of energy intake leading to significantly low body weight,” “intense fear of gaining weight or of becoming fat” and “undue influence of body shape and weight on self-evaluation” (10). The DSM-5’s assumption that the illness is proximally caused by patients’ restrictive food choices rather than by weight loss itself is outdated. Researchers in Germany have shown that a critical fall in leptin, the hormone that represents fat stores to the brain, triggers a cascade of neurobiological changes in rats, mice and AN patients that lead to food restriction and hyperactivity (11, 22-25).
Weight loss, not restrictive eating choices, is the trigger for anorexia in the genetically susceptible. It seems to patients and observers that AN is due to “persistent restriction of energy intake” because today the triggering weight loss is often the result of weight loss dieting. However, clinicians have long observed that anorexia nervosa symptoms can also be initiated by inadvertent weight loss (17, 26). This is especially common in 12- to 14-year-old girls when height increases faster than weight; girls that lose additional weight from illness or over-training can suddenly find themselves terrified of gaining weight although not previously trying to lose weight (17, 27). Multiple pathways can lead to weight loss, including growth spurts, illness, surgery, trauma, and dieting.
Fear of fat is a recent explanation
Listing fear of fat as a core and causally explanatory symptom is another inaccuracy of the DSM. Before the mid 1960s patients rarely mentioned a fear of being fat to explain food restriction and hyperactivity (28). Historically, reports of an AN-like syndrome have surfaced whenever Europeans, Asians or Indigenous Americans have starved for any reason (29). In each era victims provided historically- and culturally-bound explanations. In the early Middle Ages the Catholic Church canonized over 100 very thin people in Italy alone, in part for their ability to live with little food and tireless activity on behalf of others (30); these “holy anorexics” believed God allowed them to renounce bodily needs. Perhaps Paleolithic scouts understood the syndrome as divinely given powers to find better lands for their band.
Most renaissance victims complained that food disagreed with them or thought they could live on air. By the Victorian era the illness was attributed to a fear of sex. Explanations blaming a patients’ ambivalence about maturation dominated medicine until the mid-twentieth century when Hilde Bruch convinced the western world that teenage girls with AN were trapped in a desperate struggle for psychological autonomy from controlling mothers (31). When culturally ideal weights for women in the industrialized world dropped to 85% of normal in the late 1960s, AN patients began to blame their food restriction and excessive exercising on fear of getting fat. Today many patients attribute their AN behaviors and cognitions to needs for control or desire to eat only certain foods.
In an important review article published in 2003, Patricia Keel and Kelly Klump cautioned against naively believing patients’ explanations for their food restriction:
Although motivations for food refusal may have differed across periods (in many cases this information is simply lacking), purported motivations may not represent the true causes of self-starvation. Instead, they may represent culturally meaningful attempts to understand an affliction that leaves women feeling unable and unwilling to eat. The extent to which fear of fat is viewed as causing AN may be, in part, an illusion. (27)
Such errors come from viewing eating behavior as always arising from conscious choice and observers’ credulous acceptance of individuals’ post hoc explanati