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Why Does Anorexia Often Lead to Excessive Exercise?

By LIDA TUNESI

Anorexia is often linked to excessive exercise, but researchers don’t exactly understand why. There are plenty of people who pay attention to their diet and physical activity who don’t suffer from the disorder, so why is the combination so harmful for others?

In a new paper in Biological Psychiatry, researchers showed that, in mice, there is a clear difference between those who are vulnerable to activity-based anorexia and those who are resistant. They also took a step toward figuring out the role of dopamine in the disorder. Professor Jeff A. Beeler (Queens College, The Graduate Center), Ph.D. students Devry Mourra, Roseanna Zanca, and Rebecca Ravenelle, Professor Peter Serrano (Hunter College, The Graduate Center), Professor Susana Mingote (Advanced Science Research Center at The Graduate Center, CUNY), and Professor Nesha S. Burghardt (Hunter College, The Graduate Center) were authors on the study.

A good model of what makes a person vulnerable to anorexia could help researchers identify genes involved in the disorder, which could one day lead to early diagnosis and treatment.

The mice had 24-hour access to a running wheel but their food access was limited to two hours a day. Some mice adapted by progressively eating more food and decreasing their time on the wheel, and were able to stabilize their weight. Other mice began running more and eating less, and started losing weight quickly. Younger mice were more vulnerable to anorexia than adult mice, a pattern also seen in humans.

Eventually, the ‘vulnerable’ mice were running even when they should have been sleeping. Researchers have seen food limitations cause shifts in circadian rhythms before, and think it might have to do with an old foraging instinct. The body is so hungry that it stays awake and goes on what is, subconsciously, a hunt for food.

Mice with higher dopamine levels were also more vulnerable than others, but that doesn’t necessarily mean one is causing the other. For example, it’s possible that the dopamine just accelerates the increase in activity that was already happening. Dopamine’s role in humans is similarly murky, and the researchers hope that more research will help clear it up.

Beyond SUM

Work By

Jeff Beeler (Professor, Psychology) | Profile 1
Peter Serrano (Associate Professor, Psychology) | Profile 1
Susana Mingote (Associate Professor, Biology, Neuroscience,) | Profile 1
Nesha Burghardt (Assistant Professor, Psychology) | Profile 1