Fruit flies eat more and sleep less when they are lonely – just like humans, according to scientists.
US researchers have found that when kept in isolation, the insects’ sleep and feeding behaviour change, which is reflected in their brain activity.
The scientists said their findings, published in the journal Nature, could in future help understand the connections between loneliness, insomnia and overeating in humans.
Professor Michael W Young, head of the Laboratory of Genetics at the Rockefeller University in New York, US, said: “Clinically oriented studies suggest that a large number of adults in the United States experienced significant weight gains and loss of sleep throughout the past year of isolation precautions due to Covid-19.
“It may well be that our little flies are mimicking the behaviours of humans living under pandemic conditions for shared biological reasons.”
For the study, the researchers analysed the behaviour of the common fruit fly.
These flies are known to be social creatures, who forage and feed in groups and sleep up to 16 hours a day.
The researchers put the flies through “lockdown conditions” that the majority of the world experienced during the Covid-19 pandemic.
They found that when a single fly was isolated from its peers, the lonely insect began eating more and sleeping less.
The researchers then conducted a genetic analysis and identified a group of genes linked to starvation that were expressed differently in the brains of the isolated flies.
A small group of brain cells, known as P2 neurons, were involved in the observed changes to sleep and feeding behaviour, the team said.
The scientists found that shutting down the P2 neurons of the lonely flies helped restore sleep and suppress overeating.
Meanwhile, boosting P2 in insects that were not chronically isolated resulted in overeating and sleep deprivation – as if they had been alone for a full week.
Professor Young said: “Flies are wired to have a specific response to social isolation.
“We found that loneliness has pathological consequences, connected to changes in a small group of neurons, and we’ve begun to understand what those neurons are doing.”