Are People on a Diet To Lose Weight More at Risk for Developing Gallstones?Yes. 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.
One major study found that women who lost from 9 to 22 pounds (over a 2-year period) were 44 percent more likely to develop gallstones than women who did not lose weight. Women who lost more than 22 pounds were almost twice as likely to develop gallstones.
Other studies have shown that 10 to 25 percent of obese people develop gallstones while on a very-low-calorie diet. (Very-low-calorie diets are usually defined as diets containing 800 calories a day or less. The food is often in liquid form and taken for a prolonged period, typically 12 to 16 weeks.) The gallstones that developed in people on very-low-calorie diets were usually silent and did not produce any symptoms. 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.
Why Does Weight Loss Cause Gallstones?Researchers believe dieting may cause a shift in the balance of bile salts and cholesterol in the gallbladder. The cholesterol level is increased and the amount of bile salts is decreased. Going for long periods without eating (skipping breakfast, for example), a common practice among dieters, also may decrease gallbladder contractions. If the gallbladder does not contract often enough to empty out the bile, gallstones may form.
Are Some Weight Loss Methods Better Than Others in Preventing Gallstones?Possibly. If substantial or rapid weight loss increases the risk of developing gallstones, more gradual weight loss would seem to lessen the risk of getting gallstones. However, studies are needed to test this theory.
Some very-low-calorie diets may not contain enough fat to cause the gallbladder to contract enough to empty its bile. A meal or snack containing approximately 10 grams (one-third of an ounce) of fat is necessary for the gallbladder to contract normally. But again, no studies have directly linked a diet's nutrient composition to the risk of gallstones.
Also, no studies have been conducted on the effects of repeated dieting on gallstone formation.
Are People Who Have Surgery To Lose Weight Also at Risk for Gallstones?You bet. Gallstones are common among obese patients who lose weight rapidly after gastric bypass surgery. (In gastric bypass surgery, the size of the stomach is reduced, preventing the person from overeating.)
One study found that more than a third (38 percent) of patients who had gastric bypass surgery developed gallstones afterward. Gallstones are most likely to occur within the first few months after surgery.
Should People Who Already Have Gallstones Try To Lose Weight?Scientists know that weight loss increases the risk of gallstone formation. However, they don't know whether weight loss increases the risk of silent gallstones becoming symptomatic gallstones or of other complications developing. In addition to painful gallstone attacks, complications include inflammation of the gallbladder, liver, or pancreas. These are usually caused by a gallstone getting lodged in a bile duct.
Although excluding people with pre-existing gallstones from a weight-loss program seems prudent, there is no evidence to support this action. If people have had their gallbladders removed, there is little risk of them having gallstones or bile problems while participating in a weight-loss program.