Speculations on the Link Between Sports and Anorexia


The Hypothesis

Endurance running can cause anorexia nervosa in an otherwise healthy young woman.

It is already established that running is a risk factor for anorexia and that the two are associated. I propose here that exercise has a greater role in the genesis of the condition than is currently accepted, and that the psychological features of the illness should be considered secondary factors, when the illness occurs in athletes.


“Why do females have to be so thin to be great?”

— amber sayer, from PR: A personal record of running from anorexia



In 2015, I finished up a book I was writing on obesity science. As a doctor working in the field, I grew ever more fascinated by the mechanisms that control human body weight. The book was largely my attempt to share a vast collection of research that goes largely unrecognized. This research shows, without a doubt, that obesity is not one's fault: internal body signals control our weight. Somewhat satisfied with where I had gotten with obesity science (yep, that's arrogance), I thought it would be easy to turn next to the problem of anorexia.

As a recreational runner, I had come across many examples of good runners becoming anorexic and it looked like a clear case of a biologically driven disease being mistaken for a psychological disorder. The much greater rate of anorexia in females vs. males (10:1 ratio in many studies) seemed to suggest a hormonal cause. So, I set out to write an explanatory book about the research that describes the underlying biology of anorexia. . . except that I found that no such research exists. Well, maybe that's a bit harsh. There is a small amount of emerging science discussing the biological basis of anorexia. But the vast majority of what's been developed in the field focuses on the psychological aspects of the disease. As neurobiology has grown more influential to our understanding of psychological illness, a view of anorexia as a "brain based medical illness" is becoming more accepted. . .


What is Sports Anorexia?

The eating disorder we usually call "anorexia" has some real nomenclature problems. Its formal name "Anorexia Nervosa" is inaccurate on both counts. "Nervosa" implies that the starvation has an entirely psychological causation, reflecting an outdated understanding of the disease. "Anorexia" is Greek for "no hunger," which is also inaccurate, since most sufferers of the condition feel hungry most of the time, they just do not respond to hunger by eating.

"Anorexia Athletica" is an older term that has never been in wide circulation, but it suits my thesis pretty well. . . 


The Activity Based Anorexia Model


This story begins, as most good medical stories do, with mice. Two mice, to be specific, have volunteered to take place in a feeding experiment. The first mouse, Norma, is housed in a simple cage equipped in the usual fashion: water bottle, feeding dish and some light wood shavings for bedding. The second mouse, Anna, is housed in a cage with water, food dish and wood chips as well. But Anna is lucky and given access to a running wheel in her cage. This is a good thing for her, because mice love to run. A healthy mouse will run about a 5k per night if given free access to either open space or a running wheel.


From a 2013 Study:


of adolescent, non-athlete boys had an active eating disorder


of adolescent, non-athlete girls had an eating disorder


of elite girl athletes, in sports for which lower weight yeilds a competitive advantage, had eating disorders


If eating disorders are so tied to athletics, and if the best athletes are the most prone, it seems likely that there is something in the training itself which brings on this disorder. Is it possible that the very changes in the metabolism that help a runner succeed are some of the same determinants of disordered eating? Setting aside cultural factors within each sport and the cultural differences that boys and girls have with regard to appearance, I believe it is worthwhile to look for biological factors that respond to exercise that might serve as mediators of the disease. For the time being, I choose to call the missing link "Factor RA" for "Running Anorexia." Below are a host of considerations regarding this theoretical factor.


Defining Factor RA

One of the things that has given me a high level of enthusiasm for researching Sports Anorexia further, is the number of possible biochemical signals that I have found in the exercise physiology literature that might be involved in driving the behavior of reduced eating. In order to sort the possibilities, it is necessary, at the outset, to create a proposed definition of Factor RA:

Factor RA is a biochemical signal, (or signals), created by the muscles, or another body organ, in response to exercise, which causes prolonged, cumulative alterations in appetite regulation, such that food is intake is diminished well below levels needed for adequate health. . .