Flies are like humans: lonely fruit flies eat more and sleep less

Many people have acquired insomnia and excess weight during the pandemic. Scientists believe social isolation is partly to blame. This is agreed by geneticists from Rockefeller University, who studied fruit flies placed in a kind of "quarantine" in test tubes: it turned out that chronic separation from the group leads to changes in gene expression, nervous activity and behavior, informes phys.org.

Drosophila, like humans, are social creatures. They forage and feed in groups, practice complex mating rituals with chanting serenades, and fight each other. This is not counting sleep, which takes 16 hours daily for flies. Drosophila are evolutionarily complex organisms, and scientists often find in them the rudiments of what mammals and humans have. This is why geneticists have turned to fruit flies to investigate the biological underpinnings of chronic social isolation.

First, scientists compared how flies react to a particular stage of isolation. After a week spent in groups of different sizes, Drosophila showed no abnormal behavior. The two flies, separated from the rest, also had no problem. But when one fly was left in isolation, it began to eat more and sleep less.

A small group of brain cells, P2 neurons, were found to influence sleep and appetite. Disabling P2 in chronically isolated flies suppressed overeating and restored sleep. The increase in P2 in flies isolated from the group for only a day caused them to eat and sleep as if they had been alone for a week. P2 neurons are probably associated with the perception of the intensity of loneliness - like a timer that counts down the duration of isolation. The combination of P2 neuron activity and social isolation causes the flies to lose sleep and overeat.

Many social animals have been observed to respond to isolation with increased appetite and insomnia. The reason for this is unclear, but loneliness probably signals uncertainty in the future and tells the body to prepare. And preparing for tough times can involve being alert to stay awake as often as possible and storing food.

This is not proof that people on lockdown ate more and slept less, literally repeating the behavior of flies. But it is quite possible that the biological mechanism that determines the response to loneliness is similar in our country.