Hungry after night of drinking? Alcohol may trigger brain’s “starvation alarm”

Beth Mole

/ CHELSEA - FEBRUARY 15: Burgers and beers at Bill's Bar on February 15, 2016 in Downtown New York, NY. (Photo by Waring Abbott/Getty Images)

Getty | Waring Abbott

It’s well documented that a night of drinking will bring on the munchies. In fact, greasy spoons in college towns nationwide have built their businesses around this phenomenon, staying open late just to serve up fried, cheesy treats to the fresh-from-the-bar crowd.

But smashed feasting is a bit of a paradox. Alcohol is, after all, a calorie-packed substance, and consuming a lot of such things usually squashes our bodies’ signals for snacking. Over the years, researchers have come up with theories to explain drunken gorging. For instance, alcohol lowers self-control, which may unleash our wild food desires. But in a new study on drunk mice, British researchers may have found the real reason.

In boozy mouse brains, alcohol specifically turned on hunger-signaling neurons that are usually only activated by starvation. With the neurons activated, the tipsy rodents ate like party animals. When researchers deactivated them, the mice stuck with their normal diets.

The study only involved mice, so it can’t tell us anything definitive about humans. But the researchers note that our brains have the same starvation circuity. And they speculate that our circuits respond similarly to alcohol. Thus, the finding, published this week in Nature Communications, may not only explain drunk dining in humans; it may also reveal yet another way alcohol messes with our minds.

For the study, researchers, led by neuroscientist Denis Burdakov of the Francis Crick Institute, first had to establish whether heavy drinking had the same hunger-inducing effect on mice as it does on humans. They reasoned that it would, writing:

Most molecular pathways associated with human obesity reside in the brain and are conserved in lower animals. Therefore, we hypothesized that [alcohol] may stimulate eating across species by distorting brain hunger signals.

To test out the idea, the researchers injected the mice with high doses of alcohol, roughly equivalent to a human drinking six pints of strong beer or nearly two bottles of wine. The researchers gave out doses three days in a row, simulating what they called an “alcoholic weekend.” Sure enough, after the induced bender, the mice ate more.

Next, the researchers peered into their brains and noted that the alcohol had activated their Agrp neurons. These are neurons associated with starvation and known to trigger rapid overeating when activated. The authors described their activation as haywire hunger regulation in the rodent’s brains, “thereby sustaining false ‘starvation alarms’ despite extracellular nutrient sufficiency.” When the researchers deactivated their Agrp neurons using a chemical trick, the rodents’ smashed snacking stopped.

“Overall,” they conclude, “our findings provide an explanation for how a commonly consumed nutrient [that’s alcohol] may generate a positive feedback on energy intake.” Other than explaining the late-night cravings of drunk college students, the researchers hope that the finding provides insights that could help study and treat eating disorders, particularly those linked to obesity.

Nature Communication, 2017. DOI: 10.1038/ncomms14014  (About DOIs).