2024-08-06 17:02:33
Are you going to exercise, or would you rather sprint to the snack bar for a milkshake? What exactly happens in our brains when making such choices has long been a mystery. But Swiss researchers have now discovered the answer: it all revolves around the relatively obscure neurotransmitter orexin.
We all know the inner struggle that sometimes arises in our minds: should we dutifully go to the gym, or skip the workout and give in to sweet and fatty temptations? According to the World Health Organization, 80 percent of young people and 27 percent of adults do not get enough exercise. Meanwhile, the number of cases of obesity is rapidly increasing among both adults and children.
The role of orexin
“Despite these statistics, many people manage to resist constant temptations and exercise adequately,” says Denis Burdakov, Professor of Neuroscience at ETH Zurich. “We wanted to understand what exactly happens in their brains that helps them make these decisions.”
In their experiments with mice, the researchers demonstrated that the messenger substance orexin plays a crucial role. Orexin is one of the more than a hundred neurotransmitters actively functioning in the brain. Other chemical signaling substances, such as serotonin and dopamine, have been discovered long ago. They are much more familiar to the general public, and their roles have largely been deciphered. Orexin, on the other hand, is different: this substance was first described only 25 years ago, and scientists are now gradually unraveling its functions.
Dopamine does not explain everything
“In neuroscience, dopamine is a popular explanation for why we do some things and avoid others,” explains Burdakov. This substance is essential for our overall motivation. “However, our current knowledge about dopamine does not explain why we decide to exercise instead of eating,” he continues. “Our brains release dopamine when we eat, but also when we exercise. There is no clear explanation for why we prefer one over the other.”
To uncover what exactly drives these decisions, the researchers devised an ingenious behavioral experiment with mice. The mice could freely choose from eight different options during ten-minute trials, including a running wheel and a ‘milkshake bar’ where they could drink a tasty strawberry milkshake. “Mice love milkshakes just as much as humans do: they are full of sugar and fat, and taste great,” Burdakov notes.
Treadmill or milkshake bar
In the experiment, the scientists compared different groups of mice: one group with an intact orexin system and another group in which the system was blocked through medication or genetic modification. The mice with an intact orexin system spent twice as much time on the running wheel and only half the time at the milkshake bar compared to the mice with a blocked orexin system.
Remarkably, there was no difference in behavior between the groups in experiments where the mice had no choice: they were equally enthusiastic about the treadmill or the milkshake bar. “This means that the primary role of the orexin system is not to control how much the mice move or eat,” Burdakov clarifies. “It seems to be more important for making the choice between the two when both options are available.” Without orexin, the decision heavily favored the milkshake, and the mice gave up exercising in favor of eating.
Narcolepsy
The researchers expect that orexin also plays a role in this decision-making process in humans. The brain functions involved are virtually the same. “It is now important to verify our results in humans,” says researcher Daria Peleg-Raibstein. This can be done by studying patients who have a limited orexin system due to their genetic background. This is the case for approximately one in two thousand people suffering from the sleep disorder narcolepsy. Another possibility is to observe people who receive medication that blocks orexin. Such medications have been approved for patients with insomnia.
“If we understand how our brains make the choice between food consumption and physical activity, we can develop more effective strategies to tackle the global obesity epidemic and related metabolic disorders,” states Peleg-Raibstein. Burdakov is happy to pass the baton to scientists engaged in clinical research with humans. His next step is to investigate how orexin neurons interact with the rest of the brain in making ‘exercise-or-snack decisions’.
How Orexin May Shape Our Future Choices in Health and Nutrition
Have you ever found yourself torn between a workout and that tempting snack? A new study by Swiss researchers unveils the significant role of orexin, a relatively unknown neurotransmitter, in making these choices. The discoveries drive attention to how our brains balance physical activity with indulgent eating, crucial as 80% of young individuals and 27% of adults globally lack sufficient exercise, contributing to rising obesity rates.
Denis Burdakov, a neuroscience professor at ETH Zürich, emphasizes the importance of understanding the neural mechanisms behind decision-making in the face of temptation. Traditionally, dopamine has been seen as a key player in motivation for both food and exercise. However, this study shows that the presence of orexin is pivotal, acting as a deciding factor in choosing physical activity over unhealthy snacks when both options are available.
In experiments with mice, those with an active orexin system preferred the treadmill over sugary milkshakes, while those with blocked orexin systems gravitated towards the treats. This intriguing finding suggests that the orexin system may not regulate how much we eat or exercise, but rather influences the choices we make when both avenues are open to us.
The implications extend beyond laboratory animals. If researchers can confirm that orexin functions similarly in humans, potential advancements in combating obesity and metabolic disorders could arise. Identifying patience with narcolepsy or other forms of sleep disorders offers a unique opportunity to examine how orexin deficiency influences life choices around food and fitness.
As researchers aim to bridge the gap between animal studies and human behaviors, the insights gained could lead to novel strategies to encourage healthier lifestyles. Understanding the brain’s mechanisms for prioritizing snacks or working out might ultimately become pivotal in addressing public health challenges in an increasingly indulgent society.