(Reuters Health) - A one-year weight loss program based on lifestyle changes can help obese people shed almost as many pounds as surgery, German researchers say.

In a study published in the International Journal of Obesity, they found women who stuck with the program lost 43 pounds, while men trimmed their weight by 57 pounds.

But more than 40 percent quit before the year was up. And even among completers, three-quarters of the weight they'd lost had crept back after three years.

"Weight regain remains the Achilles' heel of all weight loss therapies," said Thomas Wadden, who runs the Center for Weight and Eating Disorders at the University of Pennsylvania in Philadelphia and was not involved in the new work.

Excess weight is one of the world's greatest health problems, tied to a host of chronic diseases, extra health care spending and early death. In the U.S., about a third of adults are obese.

While weight loss surgery effectively helps people slim down, complications and cost make the procedure less than ideal.