According to a new study published this week in Nature Communications, the great mystery of why a night of drinking always ends in devouring an entire pizza (and nachos, and fries, and more pizza) has finally been solved.
Alcohol intake is associated with overeating—so much so that it's become a recognized clinical concern. But, as researchers from the Francis Crick Institute in the UK write, "its causes are puzzling, because alcohol (ethanol) is a calorie-dense nutrient, and calorie intake usually suppresses brain appetite signals." So they set out to see if there were any biological factors at play by analyzing how the brains of mice interact with alcohol.
First, researchers had to confirm that ethanol (EtOH) really does cause overeating. "In an 'alcoholic weekend' experiment, each animal was given EtOH for three days, and saline for 3 days before and after," the study states. "The food intake was significantly and reversibly increased on the EtOH days, and the magnitude of this increase was similar in males and females." As a result, it was determined that "alcohol-induced overeating is an evolutionarily conserved biological phenomenon occurring across mammals, irrespective of aesthetic beliefs and social conditioning."
Upon further study of the Agrp neurons, which are located in the hypothalamus and have been found to cause intense hunger pangs, researchers found that alcohol activated these neurons, sending out "false 'starvation alarms' despite extracellular nutrient sufficiency," causing the mice to overeat. When they suppressed or turned off those neurons, alcohol no longer impacted the mice's desire to eat.
"Thus, we propose that the alcohol-associated activity of Agrp neurons—mediated either by direct alcohol actions described here, or via a still-unknown upstream element—is the critical step in alcohol-induced overeating," the study concludes.
Craig Blomely, one of the researchers on the study, says the main takeaway from the study is that "appetite can be hard-wired or neural in origin, rather than 'societal' or 'cultural.'" It's important to understand how the neurons in mammals' brains that push them to eat or drink work, he tells Broadly, because "it make help solve major illnesses of today, like obesity or diabetes."
If there isn't yet a tried and tested way of not getting the munchies after consuming alcohol, Sarah Caines, another author of the study, suggests maybe just getting more active to help negate the consequences. "We probably evolved to exercise at least a couple of hours per day," she says. "Subject your thus-evolved body to inactivity, and eating and drinking will get the better of you."