This weight cycling, also known as "yo-yo" dieting, has been vilified over the years. Studies have linked it to everything from high blood pressure and high cholesterol to diabetes and depression.

In fact, a 2006 review in theInternational Journal of Obesityby Swiss researchers of the scientific evidence noted an association between weight fluctuations and cardiovascular disease and death.

"I agree that data on weight cycling are mixed, particularly on weight regain, decreased energy expenditure, etcetera," said lead author Dr. Jean-Pierre Montani, professor and chair of physiology at the University of Fribourg.

"However, there is increasing evidence that weight cycling may lead to cardiovascular and metabolic disorders," such as hypertension and diabetes, he added. "And the risk of complications of weight cycling seems greater in people with normal weight or slightly overweight than in obese people."

But other experts say the news on weight cycling may not be as bad as it seems, and it shouldn't discourage people from trying to lose weight.

"From my perspective, it's so worth it to try (losing weight), even if it's the sixth time," said Dr. Michael L. Dansinger, an assistant professor of medicine and obesity researcher at Tufts-New England Medical Center in Boston. "It's the people who never give up trying who are eventually going to succeed."

Weight cycling can refer to a small weight loss and regain of 5 to 10 pounds, or a large cycle of 50 pounds or more, according to the Weight-control Information Network, a service of the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.

And at least some of the studies suggesting that repeatedly losing and gaining weight poses health risks fail to separate intentional weight loss from unintentional weight loss, one expert maintained.

"People who lose weight unintentionally may be losing weight due to a disease, such as cancer, or depression," explained Alison E. Field, associate professor of pediatrics in the Division of Adolescent Medicine at Children's Hospital Boston. "Those weight losses one would expect to look bad for your health, because they are the result, not the cause, of disease."

Field, who studies intentional weight loss, added, "In our ongoing work, weight cyclers do not appear to be more likely to die."

The U.S. National Task Force on the Prevention and Treatment of Obesity found that, while conclusive data regarding the long-term health effects of weight cycling are lacking, the potential risks do not outweigh the potential benefits of weight loss in significantly obese patients.