Several studies have shown that women with a BMI of 30 or higher have at least double the risk of developing gallstones than women with a BMI of less than 25. Why obesity is a risk factor for gallstones is unclear. But researchers believe that in obese people, the liver produces too much cholesterol. The excess cholesterol leads to supersaturation in the gallbladder. People who lose a lot of weight rapidly are at greater risk for developing gallstones.
Gallstones are one of the most medically important complications of voluntary weight loss.
The relationship of dieting to gallstones has only recently received attention. Women who lost more than 22 pounds were almost twice as likely to develop gallstones. However, about a third of the dieters who developed gallstones did have symptoms, and a proportion of these required gallbladder surgery. In short, the likelihood of a person developing symptomatic gallstones during or shortly after rapid weight loss is about 4 to 6 percent. This estimate is based on reviewing just a few clinical studies, however, and is not conclusive.