Hunger May Hasten Alcohol Cravings, Study Suggests

Hungry Fruit Flies Chase Alcohol Smells Three Hours Sooner

A bar sign passed every evening can go unnoticed day after day, then look inviting the day lunch gets skipped. Karla Kaun, the Brown University neuroscientist whose lab ran the study, uses that scenario to explain the research. Hungry flies started chasing an alcohol-linked smell about three hours sooner than well-fed ones. The researchers traced the change to a single brain cell called VUMa3, which ramps up its activity as hunger builds.

Published in Current Biology, the study found that fed flies still learn to seek out alcohol-linked smells, but through a separate route that does not need VUMa3. Hunger opens a second path to the same result, as if an empty stomach adds another way for a fly’s memory to turn a smell into a reason to go find alcohol.

Fruit flies are a useful stand-in because their brain cells can be studied one at a time. VUMa3 runs on octopamine, the fly version of norepinephrine, a human brain chemical involved in hunger and in alcohol’s effects. Lewis Sherer, a postdoctoral researcher at Brown and a study first author, described the fly work as “a step forward to understanding how humans associate cues with alcohol.”

Hungry Fruit Flies Seek Alcohol Three Hours Early

Researchers trained groups of 30 male fruit flies, collected a day or two after hatching, to pair one smell with intoxicating alcohol fumes while a second smell came without alcohol. Training ran three times, with 50-minute breaks. Hungry flies lived on nutrient-free agar, a plain gel, from before training until testing, while well-fed flies received yeast after training.

In a Y-shaped maze, flies climbed toward one of two smell streams, with each result reflecting about 60 flies.

Soon after training, flies avoided the alcohol-linked smell. Over a day, that avoidance flipped to attraction, as the memory of alcohol shifted from unpleasant to rewarding. Hunger moved up the flip by about three hours. By 24 hours, hungry and well-fed flies preferred the smell about equally.

Octopamine mattered only when flies were hungry. Flies unable to make it, or with their octopamine neurons silenced, showed weaker alcohol preference at the 24-hour test, while well-fed flies were unaffected.

A Single Neuron Called VUMa3 Ramps Up With Hunger

Octopamine is made by many brain cells, so researchers silenced smaller groups with genetic tools. One tool weakened alcohol preference in hungry flies only. A second tool, meant to hit the same cells, did nothing. Comparing the two closely revealed that the first catches one extra cell, VUMa3. Control tests showed the silenced flies could still smell normally and move as usual.

Brain imaging in living flies then showed VUMa3’s resting activity climbing in hungry flies, with a clear rise at the same point behavior began to flip. Flies that could not make octopamine showed no such rise. When hungry flies were tested a day after training, VUMa3 lit up for the alcohol-linked smell but not the other one, and fed flies showed no difference. Imaging groups held 8 to 14 flies each.

Turning On Hunger-Linked Cells Mimics Part of the Effect

To test whether activating these cells could speed things up, researchers used a heat-triggered genetic switch in well-fed flies. Early avoidance of the alcohol-linked smell dropped, and the effect vanished in flies unable to make octopamine. Movement and the 24-hour preference stayed unchanged.

That tool switches on VUMa3 and also VPM4, a neighboring cell that connects to it. Switching on VPM4 alone had a similar effect. VPM4’s own activity did not change with hunger, so VUMa3 remains the likely driver, though this experiment alone cannot isolate it.

VUMa3 also appears to keep itself revved up. It carries a receptor that responds to octopamine, the chemical it releases, and lowering that receptor’s levels cut alcohol preference in hungry flies but not in fed ones.

Hunger Opens a Backup Brain Path to Alcohol Cravings

Tracking where VUMa3 sends its signals led to the mushroom body, a fly memory center. The neuron’s branches spread widely across the brain, a pattern the authors compare to norepinephrine cells in other animals. Silencing neurons connected to that region dulled alcohol preference in well-fed flies too, so both kinds of flies lean on the same memory center.

Kaun, an associate professor of neuroscience, said the takeaway is that hunger can recruit new neurons into the circuits that tie everyday cues to alcohol’s reward. The team says the work could inform treatment and prevention, and clarify how stressors such as food insecurity shape reward systems. Sherer went further, saying a person raised in conditions of intense hunger or stress “might have a higher propensity to develop an alcohol addiction.” Fly experiments did not test that claim.

Alcohol seeking in these flies has a hunger-only route, and one neuron sits at the switch. Whether people have anything similar is unknown, because the work stopped at fruit flies and measured odor preference, not a felt urge. Still, a bar sign ignored on a full stomach and noticed on an empty one now has a concrete circuit to study.

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Disclaimer: This article is for informational purposes only and is not medical advice. The research described was conducted in fruit flies and has not been shown to apply to humans. Anyone concerned about their alcohol use should speak with a qualified health professional.

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