Dieting, weight loss, and gallstones
Dieting that leads to rapid weight loss may bring on gallstones. The risk of gallstones appears to be greater in people who lose more than 3 pounds per week than in those who loss weight more slowly.
Doctors don't know exact how dieting and weight loss might lead to gallstones. However, some experts have proposed that stringent dieting alters the balance of bile salts and cholesterol in the gallbladder. Bile salts contain large amounts of cholesterol that is "packaged" in a way that prevents it from forming stones. But in dieters, the amount of bile salts available to store cholesterol decreases, while levels of "free" cholesterol rise -- increasing the risk that gallstones will form.
In addition, eating a very low fat diet or going for long stretches between meals (e.g. skipping lunch), may decrease gallbladder contractions so the gallbladder does not empty normally. Cholesterol-based gallstones can form when bile is stored for long periods of time.