Of Portly Flies and Slimmer Thighs

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You think you've got troubles trying to zip your pants after one too many trips to the buffet table? Try having six thighs that rub together. That's what fruit flies must contend with when they over indulge on a diet that's high in fat and calories.

It turns out that even the humble Drosophila is subject to obesity and many of the same metabolic diseases as we humans are, including high cholesterol and diabetes when they make poor dietary choices. Who knew?

There are of course some disparities in the way fruit flies and people pack on the pounds. For one thing, flies are limited in the amount of weight they can gain by their exoskeletons. Carl Thummel, a professor of human genetics at the University of Utah School of Medicine who studies such things for a living, says that if you put fruit flies on a high fat diet and come back a week later to measure how large they've grown, they will be twice as heavy as the control flies that have been subsisting on a lean diet.

"We cannot tell which flies are fat simply by looking at them but that's because we're not fruit flies," he says. "I think if you were a fruit fly in the same vial you might look at them and go, 'Whoa they're fat!'"

One can only imagine the fruit fly equivalent of Maura Kelly and the gaggle of Marie Claire editors edging away from the portly Mike and Molly flies in disgust. But I digress...

Despite the differences, our insect friends can shed light on our struggles with weight. Fruit flies use the same molecular mechanisms as humans to help maintain proper balances of cholesterol and a key form of stored fat that contributes to obesity. As researchers try to learn more about the genetic and biological processes through which people regulate cholesterol and fat metabolism, flies can teach us much about ourselves.

"We don't know a lot about how these mechanisms work in humans, so by studying them in flies we can start to apply what we learn to human models," Thummel says.

Fruit flies are easier to manipulate genetically and less expensive to study than mice, chickens and dogs, all of which are also often used to study obesity -- and all of which are also easily plumped up both in and out of the lab when subjected to lots of junk food. (For the record, Thummel notes there is nothing quite as disgusting as an obese mouse.)

And believe it or not, flies share many of the same genes with humans that dictate leaness and fatness. In Thummel's own studies, he's been able to turn chubby flies svelt and back again by switching on specific genes and silencing others. Thummel, as well as other researchers, has been able to induce metabolic conditions such as high triglycerides, high cholesterol and diabetes in flies too. Considering the rate of diabetes is predicted to triple by the year 2050 -- among humans anyway -- there is much value in what we can learn from this lowly creature.

Struggle Against Obesity Ages Old

Perhaps even more importantly, fruit flies studies reveal just how long this battle of the bulge has been waged. For humans, it appears to be an ancient struggle inherited from our invertebrate ancestors. There is some comfort knowing we share with the same pests we clean off our windshields an uncontrollable biological drive to eat more than we should and bloat up past the point that's good for our health. Neither of us can help it. It's hard coded into our DNA.

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