Illustration: Edwin Fotheringham

Number of dieters: Low carb, 109; low fat, 104; Mediterranean, 109.

Pounds lost at six months: Low carb, 14; low fat, 10; Mediterranean, 10.

Final loss (two years): Low carb, 12 pounds; low fat, 7; Mediterranean, 10.

The details: Most of the dieters in this 2008 study published in The New England Journal of Medicine (and paid for in part by the Atkins Research Foundation) were men. The women actually lost more pounds on the Mediterranean approach, but the finding wasn't conclusive. As is true in most diet studies, weight loss peaked at around six months, after which dieters began to put pounds back on. All groups saw improvements in cholesterol, insulin, glucose, triglyceride, and blood pressure levels.