Illustration: Edwin Fotheringham

Number of dieters: Low carb, 77; low fat, 79; Zone, 79; Ornish, 76.

Pounds lost at six months: Low carb, 14; low fat, 9; Zone, 6; Ornish, 6.

Final loss (one year): Low carb, 10 pounds; low fat, 6; Zone, 4; Ornish, 5.

The details: Low-carb (Atkins) was ahead at six months in this 2007 study published in the Journal of the American Medical Association. But after a year, the difference in the amount of weight lost wasn’t considered significant between the low-carb, low-fat and Ornish diets (the Zone group came out last). However, low-carb dieters saw their heart disease risk factors—blood pressure, cholesterol, triglyceride levels—improve at least as much as the people on the heart-healthy low-fat and Ornish diets. Again, most of the pounds were shed in the first few months, with many people gaining back some weight. By the end, in fact, many in all four groups had stopped following their prescribed diets closely.