New research shows that exposing rats to a context associated with eating chocolate activates a part of the brain’s reward system known as the orexin system; this helps explain why eating can be triggered by environmental cues even in the absence of hunger. The findings could help scientists develop new drug treatments for overeating. As the rate of obesity steadily rises in the United States and abroad, researchers are trying to find out more about how palatable foods affect the brain. It seems that especially tasty foods elicit brain responses similar to those elicited by drugs such as cocaine and nicotine, pointing to a general involvement in the brain’s “reward” system. Science Daily reports that research to be presented at the Annual Meeting of the Society for the Study of Ingestive Behavior (SSIB) shows that a common factor may be activation of orexin neurons in the brain, which are recruited during rewards such as a tasty food or a dose of cocaine. “Our research program is focused on identifying brain systems that are activated by palatable food intake. The hypothalamic orexin system is known to promote wakefulness and arousal; however, it is now clear that this system also participates in the regulation of reward-related behaviors, including overconsumption of palatable foods,” says Derrick Choi, Department of Psychiatry at the University of Cincinnati and lead author of the study. Because reward anticipation is a contributing factor to relapsing for drug and alcohol addicts, Choi hypothesizes that orexin is an ideal candidate system that may underlie the rewarding aspects of eating highly palatable foods, which clearly can lead to obesity. The researchers trained rats to expect a piece of milk chocolate in a unique environment. After training, the rats were placed into the same environment where no chocolate was present. They found that the expectation of chocolate alone activated brain orexin systems, which could explain why some people tend to overeat in contexts associated with past experiences of eating tasty food. “It entirely possible that future treatments for obesity will involve a combination of lifestyle changes as well as pharmacological therapies aimed at orexin and other brain systems, to regulate food reward-related behaviors,” said Choi.
