Alcohol affects the brain's response to food aromas and increases food consumption in women

Alcohol sensitizes the brain's response to food aromas and increases food intake—known as the aperitif effect—according to a new study by researchers at Indiana University School of Medicine in Indianapolis.

Indeed, this study showed that increased food intake does not rely entirely on the oral ingestion of alcohol and its absorption through the gut. The brain—particularly the hypothalamus—may be a site of action for the aperitif effect.

"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," said William J. A. Eiler II, PhD, of the Indiana University School of Medicine's Departments of Medicine and Neurology. "Many alcoholic beverages already include empty calories, and when you combine those calories with the aperitif effect, it can lead to energy imbalance and possibly weight gain."

The study appears in the July issue of the journal Obesity, published by The Obesity Society (TOS).

“Given the rise in reported alcohol consumption, particularly wine, in the United States, overeating following alcohol consumption may contribute to weight gain and significant health-related consequences,” the authors wrote. “While increased food consumption following an aperitif appears replicable, the mechanism remains unclear.”

In an attempt to uncover such a mechanism, the researchers recruited 35 non-vegetarian, non-smoking, non-obese women for their study. To test the direct effects of alcohol on the brain prior to eating, 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. Participants were observed, and brain responses to two food aromas (Italian meat sauce and roast beef) and a non-food aroma (Douglas fir) were measured using blood oxygenation level dependent (BOLD) response via fMRI scans. After imaging, participants were offered a lunch choice between pasta with Italian meat sauce or beef and noodles.

Results showed that when participants received IV alcohol, they ate 7% more food at lunch on average compared to when they were given the placebo.

In addition, brain scans showed that the hypothalamus responded more to food odors compared to non-food odors after alcohol infusion. 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.

However, there were individual differences, with one-third of participants eating less after alcohol exposure when compared to the placebo exposure.

"Often, the relationship between alcohol on eating is oversimplified; this study unveils a potentially more complex process in need of further study," noted Martin Binks, PhD, FTOS, Associate Professor of Nutrition Sciences at Texas Tech University in Lubbock, Texas.

To that end, the study authors called for further research to investigate the mechanism by which the hypothalamus affects food reward.