Sport or snacking? Here's how our brain makes the decision

Researchers at ETH Zurich have discovered that orexin, a chemical messenger in the brain, plays a crucial role in choosing between physical exercise and snacking. This finding could help develop strategies to encourage physical activity in people who struggle to motivate themselves to exercise.


Neuroscientists conducted an experiment with mice to understand how orexin influences this decision. The mice had the choice between running on a wheel or enjoying a strawberry milkshake. When their orexin system was blocked, the mice overwhelmingly preferred the milkshake over exercise. In contrast, mice with an intact orexin system spent more time running than drinking the milkshake. This indicates that orexin helps mediate between exercise and food when both options are available.

Orexin, less known than other neurotransmitters such as dopamine and serotonin, was discovered about 25 years ago. Its role in appetite regulation is becoming better understood. However, its function in the choice between eating and exercising is a recent revelation. Denis Burdakov, a neuroscience professor at ETH Zurich, explains that while dopamine is often associated with motivation, it does not explain why we sometimes prefer exercise over food, since both activities stimulate the release of dopamine.

In the experiment, the researchers compared the behavior of two groups of mice: one with a functional orexin system and the other with an orexin system blocked by a drug or genetic modification. The results show that without orexin, the mice chose food over exercise twice as often. However, when the mice were only given one option, either to run or to eat, their behavior was surprisingly similar.

These results, although obtained from mice, are likely transferable to humans, as the brain functions involved are similar in both species. People with a restricted orexin system, such as narcoleptics or those treated for insomnia, could provide valuable insights in future research.

This research paves the way for new strategies to combat obesity and metabolic disorders by better understanding how the brain decides between eating and exercising.