Killer Workout

What happens when exercise goes too far? Learn about activity anorexia.

By Nancy Dess, published on May 1, 2000 - last reviewed on June 9, 2016

The virtues of dieting and physical fitness pervade our
consciousness. But either can go too far, leading to self-starvation or
compulsive exercising--or both. In fact, one may actually cause the
other, warns W. David Pierce, Ph.D., of the Sociology and Neuroscience
faculties at the University of Alberta. Here, he discusses a dangerous
and increasingly pervasive phenomenon called "activity anorexia."

Nancy K. Dess: What is activity anorexia?

W. David Pierce: Activity anorexia is a problematic behavior
pattern in which a drastic decrease in eating causes progressively more
exercise, which further reduces eating, in a vicious cycle.

NKD: How have you studied this in the laboratory?

WDP: In a typical experiment, rats live in a cage with a running
wheel. At first, they can eat and run freely. Then they are shifted to
one daily meal. Rats with no chance to run stay healthy, but rats allowed
to run develop startling effects: Their running increases from hundreds
to thousand of revolutions per day, and their eating decreases. Not all
rats develop this pattern to the same degree, but many would die if it

NKD: Why does this happen?

WDP: Consider Darwin's theory of evolution through natural
selection. Animals would have gained a survival advantage by migrating
when food was scarce, and by staying on the move until an adequate supply
was found. A trek moved them away from famine and increased the odds of
finding food--and surviving to pass on this trait.

We've shown that as food becomes scarce, rats, especially females,
will work harder to earn a chance to run. Thus, events in the distant
evolutionary past can be traced to a behavioral reinforcement

NKD: How does that play out for humans in contemporary

WDP: Our culture brings dieting and exercise together. Current
cultural values of thinness and fitness ensure that many
people--especially women--receive social reinforcement for dieting and
exercising. At some point, for some people, the eating/activity
mechanisms begin to operate independently of culture. Their original
goals or motivations become irrelevant.

NKD: What about anorexia nervosa, which is clinically diagnosed on
the basis of extreme thinness, fear of fat and distorted body image. How
is that related to activity anorexia?

WDP: Professionals' definitions make them sound completely
different, but they may not be. The diagnostic criteria for "anorexia
nervosa" focus on what people think and feel--about themselves, their
bodies, and so forth. Activity anorexia is about what people do--how much
they eat and exercise. My colleagues and I have argued that most cases
diagnosed as anorexia nervosa, a "mental illness," are actually cases of
activity anorexia, a problematic behavior pattern. You see, what people
consciously think can be misleading.

NKD: For example?

WDP: A Canadian woman denied exercising but said she liked to walk.
When asked where she walked, she replied, "To..."

NKD: Cleveland.

WDP: Basically, yes. To the mall--five kilometers away, four or
five times a day. She didn't think of it as exercising. So careful
assessment of actual behavior, in addition to what people think or feel,
is critical.

NKD: But does it really matter how we define the problem?

WDP: I think so. Of those receiving a diagnosis of anorexia
nervosa, between 5% and 21% will die. If eating and exercising are
central to the problem, then more attention should be focused on these
behaviors. Specifically, sudden changes in exercise or eating--"crash"
dieting--are warning signs, at least as important as a desire to be thin.
Understanding this problem fully is key to figuring out how to prevent it
or treat it effectively--which is literally a matter of life and