The doctors, naturally, measured the women's sensitivity to insulin and the rate of glucose uptake in their muscles, which previous researchers have claimed stimulates an enzyme that burns fat.
Reports Klein: "It's the most sensitive approach we have for evaluating insulin in people. And we were unable to detect any effect of resveratrol."
But what about the individual body cells? Well, Klein took samples of the women's muscle and fat tissue. And again, no sign of resveratrol.
Do you hear that? These supplements -- upon which Americans spend $30 million annually -- have no effect whatsoever.
That's not to say resveratrol isn't the agent of red wine's wonder powers, Klein adds. It's just that it has to work in concert with other compounds in red wine.
The moral of this story? Keep drinking.