Neuroscience unveils why diet and exercise are more than just willpower

A recent study at ETH Zurich sheds light on why the choice between exercise and indulging in a treat isn't just a matter of willpower. The study reveals that a brain chemical called orexin plays a crucial role in tipping the balance between physical activity and indulgence.

The study, conducted on mice, highlights orexin's influence on decision-making, particularly when faced with the option of exercising or enjoying a sugary snack. Mice with an impaired orexin system were more likely to choose the treat over exercise, suggesting that orexin could be a key factor in promoting physical activity.

The question of why we sometimes opt for a workout over a tempting treat has puzzled scientists for years. This research suggests that orexin and the neurons that produce it are at the heart of this decision-making process.

Professor Denis Burdakov, a leading neuroscientist at ETH Zurich, explains, “We’ve always wondered what helps some people resist temptation and stay active while others struggle. Our research shows that orexin might be the missing piece of the puzzle.”

Orexin is one of many chemical messengers in the brain, but its role in decision-making is unique. While other well-known chemicals like serotonin and dopamine have been studied extensively, orexin is relatively new to the scene, discovered only about 25 years ago.

To explore orexin's role, the researchers designed an experiment where mice could choose between running on a wheel or drinking a strawberry-flavored milkshake. The results were telling: mice with an intact orexin system spent more time exercising and less time indulging in the milkshake. In contrast, mice with a blocked orexin system preferred the milkshake, showing less interest in the wheel.

Interestingly, when only one option was available—either exercise or the milkshake—the mice’s behavior didn’t differ between the groups. This suggests that orexin isn’t about controlling how much we eat or move but rather about guiding our choices when we have competing options.

The implications of this research extend beyond mice. Since the brain functions similarly in humans, the findings could pave the way for new strategies to encourage physical activity and combat obesity. The researchers plan to verify their results in humans, particularly in individuals with conditions affecting the orexin system, such as narcolepsy.