Belinda Smith
Belinda Smith is a science and technology journalist in Melbourne, Australia.
A pie or hot dog scoffed at 3 am is, quite simply, delicious. But why do we crave fatty and carb-rich food after drinking alcohol, which itself laden with kilojoules? It turns out the brain cells that make you hungry are also activated by alcohol.
Researchers in the UK put mice on the equivalent of a human weekend bender and found their subjects ate more food than teetotal counterparts. Examining the mouse brains, the team found a specific set of brain cells that drive hunger were activated in the presence of alcohol.
The work was published in Nature Communications.
Alcohol consumption and overeating are linked. Drinking an aperitif before a meal stimulates the appetite. Why, though, is a puzzle.
Eating energy-rich food usually stops the hunger signal in the brain and alcoholic drinks are usually packed with kilojoules.
For instance, a bottle of full-strength beer contains around 550 kilojoules and a gin and tonic, around 800 kilojoules. The average daily energy requirement for a middle-aged woman is 8,000 kilojoules, and just shy of 10,000 kilojoules for men of the same age.
So why the appetite after a night propping up a bar?
To find the underlying neural drivers of this behaviour, Sarah Cains and Craig Blomeley, both from the Francis Crick Institute, and colleagues gave mice an “alcoholic weekend” – the mouse version of ethanol reported to be consumed by more than a quarter of young UK people at least once a week, around 18 30-millilitre shots of spirits, over three days.
Another group, the controls, drank saline solution.
The researchers weighed the food eaten by both groups. Not surprisingly, the boozy mice ate significantly more food on their bender than the control group. This rise in consumption dropped again once the weekend was over, and the magnitude of the increase was similar in males and females.
Taking a look at slices of the mouse brains, Cains, Blomeley and their crew found a population of neurons called Agrp, which form part of the mouse brain’s feeding circuit, were activated in the presence of alcohol.
To see if these neurons were indeed responsible for overeating in the animals, the team took another set of mice, “silenced” their Agrp neurons with a small molecule called clozapine-N-oxide, and then put them on an alcoholic weekend.
They found this cohort didn’t overeat, showing Agrp cell activity is essential for alcohol-induced overeating.
So the next time you find yourself queueing for hot chips and gravy at 3 am, you have your brain’s feeding circuit to thank – or curse.
