Cynthia Kenyon, 55
Geneticist, Department of Biochemistry and Biophysics, University of California–San Francisco
What she does: Follows a "low glycemic index" diet, which limits foods that the body quickly converts to sugar. That means minimal pasta, potatoes, bread, and rice, and no dessert (well, an occasional morsel of dark chocolate). She now subsists on chicken Caesar salads, broccoli with peanut oil, asparagus, fish, a little red meat, and red wine.
Why: To keep her blood sugar from spiking and triggering corresponding insulin surges. The former admitted sweets addict revamped her diet after discovering in 2002 that feeding roundworms sugar cut their lives by 20 percent. Sugar promotes insulin, which turned off a "longevity gene" that Kenyon had previously found could be activated to double the worms' normal three-week life span. An equivalent gene exists in people (it, too, is deactivated by insulin). Versions of it have been linked to the ability to reach 100.
[Read about 4 diets that are really good for you.]