Social isolation causes flies to eat too much and sleep too little

According to a new study published in Nature, chronic social isolation causes overeating and sleep reduction in fruit flies (Drosophila). Scientists discovered that, compared to flies living in social groups, those quarantined for over a week in test tubes start eating too much and sleeping too little. 

“Flies are wired to have a specific response to social isolation,” said Professor Michael W. Young, head of the Laboratory of Genetics at Rockefeller University. “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.”

A team from Young’s lab, led by researcher Wahne Li, discovered that a small group of brain cells known as P2 neurons were responsible for the observed changes in sleep and feeding behavior of the fruit flies. “The P2 neurons seem to be linked to the perception of the duration of social isolation, or the intensiveness of loneliness, like a timer counting down how long the fly has been alone,” Li explained. 

By describing how chronic separation from a social group leads to significant changes in neural activity and behavior in flies, this study provides a powerful model for investigating the body’s biological reaction to loneliness. Further research is needed to fully understand the complex connections between loneliness, overeating, and insomnia in other animals and, eventually, in humans.  

“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,” said Professor Young. “It may well be that our little flies are mimicking the behaviors of humans living under pandemic conditions for shared biological reasons.”

Although these reasons are not yet perfectly clear, a possibility could be that social isolation indicates a degree of uncertainty about the future, Young claimed. Preparing for the possibility of difficult times ahead might include being awake as much as possible and eating whenever there is food available.  

More research on the biological and psychological effects of social isolation could open new pathways for mitigating them and for learning how to better cope with various stressful conditions. 

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By Andrei Ionescu, Earth.com Staff Writer