Obesity is an increasing public health problem. As a consequence, many people attempt to lose weight by dieting or participation in weight loss programmes. Weight loss is associated with an increased risk of symptomatic gallstones. Preventive measures include keeping the rate of weight loss below 1.5 kg per week, and providing a fat intake of at least 7 g a day. If it is expected that the rate of weight loss will be faster or difficult to control, for example after bariatric surgery, prophylaxis with ursodeoxycholic acid may be considered.