Popular Science’s “Ask Anything” column must get the most bizarre requests for information throughout the year, but here’s one that’s mildly amusing. I like to think of the answer as the ultimately pair of jeans. Ever see a movie, commercial or real life example of someone jumping up and down squeezing themselves into a pair of jeans. That analogy is at the heart of the answer to whether insects can suffer from obesity. Really!
Scientists have actually studied weight gain, obesity and diabetes in insect. In the early 60’s a Florida entomologist studied obese mosquitoes. More recently, scientists have studied obesity in male dragonflies. Ruud Schilder, a biologist at Penn State, showed that infection with a certain parasite will induce the bugs to build up lipids in their thorax and around the muscles that they use for flight. The most extensive work on insect obesity has been done on fruit flies. Larvae fed high-calorie diets tend to fatten up quickly, though ones with high-sugar diets develop a condition similar to diabetes and suffer shortened lifespans. Once a fly reaches adulthood, though, there’s a limit to how big it can get. Just like a human, the fruit fly stores its excess energy as lipid droplets, which are encased in cells. (Our lipid droplets live in fat tissue; a fruit fly has a comparable organ called the “fat body.”) But grown-up flies, like other insects, are encased in a chitin exoskeleton. That means their bellies can’t expand, says Thomas J. Baranski, an endocrinologist at Washington University. “Because it’s got this exoskeleton, it just packs the fat in tighter.”