NEW YORK (Reuters Health) - Men who successfully lose weight, regain it, lose it again and so on -- a pattern called weight cycling -- are at increased risk of developing gallstones, research shows.

Gallstones -- solid masses of cholesterol, bile and calcium salts that form in the gall bladder -- are common among adults in Western countries. While most gallstones produce no symptoms and dissolve naturally, others can cause painful blockages that require intervention.

Dr. Chung-Jyi Tsai of the University of Kentucky Medical Center in Lexington and colleagues studied ties between weight cycling and gallstones among 24,729 men in the ongoing longitudinal Health Professionals Follow-up Study. The men provided information on weight fluctuations between 1988 and 1992 and were followed for gallstones until 2002. The mean age at the beginning of the study was 55 years old.

Overall, 1,222 cases of painful gallstones occurred between 1992 and 2002.

Gallstones were more likely to develop in weight cyclers than in weight maintainers -- that is, men who remained within 5 pounds of their initial weight between 1988 and 1992.

Light weight cyclers -- men who lost between 5 and 9 pounds per attempt -- had a 21-percent increased risk of developing gallstones, whereas moderate cyclers (weight loss between 10 and 19 pounds) had a 38-percent increased risk of gallstones.

Severe weight cyclers (men who lost 20 pounds or more per attempt) had a 76 percent increased risk of developing gallstones.

More frequent weight swings also increased gallstone risk: two or more weight cycles increased the risk by roughly 30 percent in men who had weight loss and gain cycles of 10 to 19 pounds, and by roughly 50 percent in men who had weight loss and gain cycles of more than 20 pounds.

These associations remained even after adjusting for body weight and other known and suspected risk factors for gallstones, suggesting that it is weight cycling rather than being overweight or obese alone that raises the risk of gallstones, the researchers note.

Consistent with prior studies, the majority of men in the study were weight cyclers not weight maintainers (17,286 versus 7,443). "Although approximately 30 percent of adult U.S. men are trying to lose weight, intentional weight loss is rarely sustained and is often associated with unintentional weight regain, leading to weight cycling," Tsai and colleagues write in their report, published in the Archives of Internal Medicine.

It's likely that multiple factors underlie the association between weight cycling and gallstone formation, they say. Studies have shown that large swings in body weight contribute to the development of metabolic abnormalities, including insulin resistance, which may facilitate gallstone formation. Weight cyclers also have higher levels of the fat-related hormone leptin and blood insulin levels, which could also contribute to gallstones.