ATLANTA — The Atkins diet may have proved itself after all: A low-carb diet and a Mediterranean-style regimen helped people lose more weight than a traditional low-fat diet in one of the longest and largest studies to compare the dueling weight-loss techniques.

A bigger surprise: The low-carb diet improved cholesterol more than the other two.

However, all three approaches — the low-carb diet, a low-fat diet and a so-called Mediterranean diet — achieved weight loss and improved cholesterol.

The study is remarkable not only because it lasted two years, much longer than most, but also because of the huge proportion of people who stuck with the diets — 85 percent.