Alcohol Sensitizes Brain Response to Food Aromas

The first study of its kind measuring the brain's role in mediating caloric intake following alcohol consumption among women shows that alcohol exposure sensitizes the brain's response to food aromas and increases caloric intake.

The research, led by William J. A. Eiler II, PhD, of the Indiana University School of Medicine's departments of medicine and neurology, adds to the current body of knowledge that alcohol increases food intake, also known as the apéritif effect, but shows this increased intake doesn't rely entirely on the oral ingestion of alcohol and its absorption through the gut. The study was published in the July issue of the Obesity.

"The brain, absent contributions from the gut, can play a vital role in regulating food intake. Our study found that alcohol exposure can both increase the brain's sensitivity to external food cues, like aromas, and result in greater food consumption," Eiler says. "Many alcoholic beverages already include empty calories, and when you combine those calories with the aperitif effect, it can lead to energy imbalance and possible weight gain."

Researchers conducted the study in 35 nonvegetarian, nonsmoking women at a healthy weight. To test the direct effects of alcohol on the brain, researchers circumvented the digestive system by exposing each participant to intravenously administered alcohol at one study visit and then to a placebo (saline) on another study visit, prior to eating. Participants were observed, and brain responses to food and nonfood aromas were measured using blood oxygenation level dependent response via functional magnetic resonance imaging scans. After imaging, participants were offered a lunch choice between pasta with Italian meat sauce and beef and noodles.

When participants received intravenous alcohol, they ate more food at lunch, on average, compared with when they were given the placebo. However, there were individual differences, with one-third of participants eating less after alcohol exposure compared with placebo exposure. In addition to changes in consumption, the area of the brain responsible for certain metabolic processes, the hypothalamus, also responded more to food odors, compared with nonfood odors, after alcohol infusion vs saline. The researchers concluded that the hypothalamus may therefore play a role in mediating the impact of alcohol exposure on our sensitivity to food cues, contributing to the aperitif phenomenon.

"This research helps us to further understand the neural pathways involved in the relationship between food consumption and alcohol," says Martin Binks, PhD, FTOS, secretary treasurer of The Obesity Society and an associate professor of nutrition sciences at Texas Tech University. "Often, the relationship between alcohol on eating is oversimplified; this study unveils a potentially more complex process in need of further study."

Study authors agree and call for further research into the mechanism by which the hypothalamus affects food reward.

"Today, nearly two-thirds of adults in the United States consume alcohol, with wine consumption rising, which reinforces the need to better understand how alcohol can contribute to overeating," Binks says.

— Source: The Obesity Society