Isolation affects even fruit flies

At least half of Brazilians gained weight during the pandemic, according to a survey by the Ipsos Institute. On the one hand, this news could be cause for celebration: since being an animal means having to search for enough food every single day (since we don't photosynthesize like plants), gaining weight by definition requires consuming more energy than you expend. Did you gain weight during the pandemic? Congratulations, you are privileged: you had more than enough food and, most likely, did not have to continue walking long distances or squeezing into public transportation, exposed to the Russian roulette of the virus. Above all, you did not die.

With the caveat that worrying about being overweight during a pandemic is a problem for the privileged, let's get to the considerations. Why would being locked up at home expose so many lucky people to this problem, when the brain in principle knows perfectly well how to regulate our appetite and food intake?

Physical inactivity is certainly a factor. In addition, I would bet that the lack of things to do in confinement is a risk factor for increased visits to the refrigerator—although I am not aware of any studies on this particular topic (and imagine that Brazilians surveyed would quickly find a way to circumvent refrigerator door opening counters in such surveys).

But not everything is the fault of our idleness or laziness: even in fruit flies, chronic social isolation is enough to make the brain hungry, according to a study conducted at Rockefeller University in the US.

Laboratory flies are usually raised in groups, always with abundant food, but they eat a stable amount of food. There is always some left over.

But after a week of continuous isolation, the flies become restless during the day—and, more importantly, eat up to three times more food. Whether they gain weight, I don't know; the researchers do not report whether they weighed the animals before and after the experiment.

But they did the hard part, which was to examine how gene expression changes with isolation. The verdict: chronic isolation leaves the flies' brains in a state of gene expression similar to starvation, despite the abundant food. There is no way of knowing whether the isolated flies feel hungry, but they certainly behave that way, eating as if there were no tomorrow—just like humans in quarantine.

In other words: if you stay home, stress gets to you; if you run, the virus gets you. What's the solution? Vaccines, of course. It's good that there are still people investing in science around the world.