Researchers have examined the role of orexin, a chemical messenger in the brain, when it comes to choosing between exercise and snacking.
- Exactly what happens in our brains when we choose between exercise and a snack has long been a mystery to science, but researchers may have just cracked it by studying the brain chemical at the heart of this decision-making process: orexin.
- The researchers conducted an experiment on mice, which were given eight different options to choose from, including a wheel on which they could run endlessly and a “milkshake bar” that they could eat as they pleased.
- “The primary role of the orexin system is not to control how much mice move or how much they eat. Rather, it appears to be essential for making the decision between one and the other, when both options are available.” Without orexin, in fact, the decision was overwhelmingly in favor of the milkshake, and the mice gave up the exercise in favor of the treat.
Should I hit the gym or should I eat that chocolate bar on the couch? Why do some people manage to resist temptation and get going, while others can’t? What exactly happens in our brains when we make these decisions has long been a mystery to science.
But a team of researchers at the Swiss Federal Institute of Technology in Zurich may have just cracked it, by studying the chemical in the brain that is at the heart of this decision-making process: orexin (and the neurons that produce it). Their work was published in the journal Nature Neuroscience.
The role of orexin in decision making in mice
Orexin, identified late about 25 years ago, is one of hundreds of chemical messengers that are active in the brain, along with serotonin and dopamine. “But current knowledge about dopamine, which is essential to our overall motivation, does not really explain why we decide to exercise instead of eating, can we read in a press release. Our brains release dopamine both when we eat and when we exercise: there is no evidence to suggest why we choose one over the other.”
To examine the role of orexin in decision-making, the researchers conducted a behavioral experiment on mice. The mice were asked to freely choose from eight different options over several 10-minute trials, including a wheel on which they could run indefinitely and a “milkshake bar” which they could enjoy as they pleased. “Rodents like milkshakes for the same reason humans do: They’re loaded with sugar and fat, and they taste good.”scientists specify.
The team then compared the different groups of animals: the first consisted of normal mice, the second of mice whose orexin systems were blocked, either by a drug or by genetic modification of their cells.
Orexin is essential for deciding between one option and another
As a result, rodents with an intact orexin system passed “twice as much time on the wheel and twice as much time on the milkshake” than mice whose orexin system had been blocked. Interestingly, however, the behavior of the two groups was similar in experiments in which the scientists offered the mice only the wheel or only the milkshake.
“This suggests that the primary role of the orexin system is not to control how much mice move or how much they eat, researchers assure. On the contrary, it appears essential to make the decision between one and the other, when both options are available.” Without orexin, in fact, the decision was largely in favor of the milkshake, and the mice gave up the exercise in favor of the treat.
According to the study, what is observed in mice is also observed in humans, “the brain functions involved here being virtually the same in both species”. If it is now necessary to verify them on humans, these results could well have “therapeutic implications for patients who have a restricted orexin system for genetic reasons – this is the case for about one in 2,000 people.”
“If we understand how the brain trades off food intake and physical activity, we can develop more effective strategies to combat the global obesity epidemic and related metabolic disorders.”the scientists conclude.
