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I don’t believe, in all my years, I have ever seen a fruit fly I would consider obese¹. But, thanks to the wonders of modern science, that’s all about to change. Because a team of researchers from Cold Spring Harbor laboratory has produced the first flies that are genetically³ engineered to overeat. 

If you are wondering…why…it’s not as silly as it might sound. A big part of weight control has to do with making healthy dietary choices and knowing when to step away from the snack cabinet. But what controls those behaviors?

Well, we humans have a hormone⁴ called leptin that tells us that we’re full. After eating, leptin is released from our fat cells. And it travels to our brains to signal that we’ve had enough. Indeed, people who don’t produce leptin…or who lack the molecular⁵ machinery⁶ to detect it…really pack on the pounds. 

In the new study, researchers discovered a hormone that acts the same way in flies. And when they deleted the gene² that encodes it, the hormonally deficient⁷ insects just kept eating. And when presented with the fly equivalent of a high-fat or high-sugar diet, they gained three times more weight than did their hormonally competent peers. The findings appear in the journal Cell Metabolism⁸. [Jennifer Beshel et al., A Leptin Analog⁹ Locally Produced in the Brain Acts via a Conserved¹⁰ Neural¹¹ Circuit to Modulate¹² Obesity-Linked Behaviors in Drosophila]

Interestingly, giving human leptin to these tubby bugs¹³ eliminates their tendency to binge. That suggests that by studying these flies, scientists might learn something that’s relevant to us.

In the meantime, researchers from the U.K. and Australia have also been plying¹⁴ flies with sweet treats. And they found that consuming large amounts of sugar may lead to fewer birthday cakes. 

In this study, researchers compared the life spans of flies that ate a healthy diet, with 5 percent sugar…to those that went on a three-week bender of 40 percent sucrose. That’s the equivalent, the researchers note, of a person who really took Marie Antoinette’s advice to heart and ate only cake for two decades.

The results? The sugar-fed flies lost about 7 percent of their already brief 90-day life span. And that was even if they reverted¹⁵ to the healthy diet after their three weeks on sweets. These results appear in the journal Cell Reports. [Adam J. Dobson et al, Nutritional¹⁶ Programming of Lifespan by FOXO Inhibition on Sugar-Rich Diets]

The sugar overload¹⁷ apparently¹⁸ triggered long-term changes in gene activity…which accelerated aging and had the sugar-buzzed flies dropping like, well, like flies.

The findings suggest that you can have your cake and eat it, too. But not for long. 

—Karen Hopkin 

[The above text is a transcript¹⁹ of this podcast.]