(FORTUNE Magazine) – If you think this story will tell you about an easy way to get rid of the 15 pounds you've piled on since college, sorry. The truly obese--that is, those who have a body mass index of 30 or more--may be able to drop up to 7% of their weight by taking Xenical or Meridia, drugs that block absorption of fat and cut appetite, respectively. But if you're merely overweight, with a BMI of 25 to 30, the only remedy is that same tiresome one you've heard all your life: Get your face out of the Cheetos and your butt on that treadmill. Losing relatively little weight--say, going from a BMI of 27 to a BMI of 24--can confer major health benefits, including lower risk of diabetes and of certain cancers. Oh, yeah: You'll look better too.

But in the 2010s, everything may be different. That's because the study of the human genome is getting researchers excited about the possibility of resetting our genetically controlled fat thermostats. The goal is to get the metabolisms of overweight people--whose genomes may predispose their bodies to store calories as fat--to behave more like those of thin people. Millennium Pharmaceuticals in Cambridge, Mass., is testing a drug in Britain that it says does just that: increases the rate at which the body burns fat. French firm Genset hopes to start human trials in 2002 for a similar drug, Famoxin. Meanwhile, Amgen in Thousand Oaks, Calif., is testing an injectable form of leptin, a hormone believed to signal the body to reduce its level of fat.

Some researchers are even convinced that a virus--yes, a virus--can cause obesity. About 30% of obese individuals screened in 2000 at the University of Wisconsin at Madison had antibodies to an adenovirus called Ad-36, raising the possibility that you may someday be vaccinated against gaining weight. Oh, happy day!

Until then, steer clear of the ice cream.

--JULIE CRESWELL