Rapid-weight-loss diets can be tempting quick fixes. You know the circumstances. You want to quickly lose a few pounds to look great in a suit or dress that you plan to wear to a reunion…or you aim to fit into a slinky gown for a wedding reception…or to look your hunky best for a vacation cruise.

You know that rapid-weight-loss and crash diets are self-sabotaging because they can mess with your metabolism and hormones, but there’s another painful reason why you should steer clear of rapid-weight-loss dieting—gallstones.

The biggest risk factor for gallstones is carrying too much weight, especially around the middle, but rapid weight loss can also bring on gallstone formation. Recent research is providing insight into how gallstones can be prevented naturally in dieters, although some dieters might not like what these researchers have to say.


About half a million Americans have their gallbladders removed each year because of gallstones. Gallstones are formed by different substances. Those that most commonly form in people who are overweight or who go on rapid-weight-loss diets are made from excess cholesterol in bile (also called gall), which is produced by the liver and stored in the gallbladder. (Bile is used as a digestive enzyme in the small intestine.) The stones can range in size from grains of sand to golf balls.

Gallstones may cause no symptoms or health problems at all—but if a stone gets stuck in a bile duct of the gallbladder, it can cause severe pain (it’s often compared with the pain of childbirth) and other complications, such as jaundice (yellowing of skin and eyes). Symptoms include sudden, rapidly worsening pain in the upper right or middle part of the abdomen or pain between the shoulder blades or under the right shoulder. The pain can last for minutes or hours and then pass. (Seek immediate attention if the pain becomes so severe that you can’t sit still or if jaundice develops.)


A recent study by German and Danish researchers led by Frank Lammert, PhD, professor of medicine at Saarland University Medical Center in Homburg, Germany, identified two ways to prevent gallstones during weight loss. One way is preventive treatment with ursodiol (Actigall, Urso), a prescription drug used to prevent gallstones and dissolve existing ones in patients who need but either can’t have or don’t want gallbladder surgery. The other way, which may sound counterintuitive, is to follow a diet higher in fat—although this isn’t how many “lose-weight-fast” dieters want to eat.

In two small published studies that Dr. Lammert and his team looked at, gallstones developed in 38% and 67% of patients on very-low-fat diets and none on higher-fat diets. Overall, Dr. Lammert’s team (which analyzed 13 published clinical trials on the topic of gallstones and weight loss) found that patients whose weight-loss diets contained between 19% and 30% fat had fewer gallstones than those whose diets contained between 3% and 5% fat. The reason? Scientists theorize that a meal that is higher in fat stimulates the gallbladder to move bile between the liver and intestines at a fast enough pace to prevent gallstone formation.


To minimize risk of developing gallstones during weight loss, the researchers concluded that losing 1.5 kg (about 3.3 pounds) a week was best. This might make some dieters impatient, but remember that slow and steady calorie control is the best way to lose weight and keep it off.

For people considering weight-loss surgery, be aware that rapid weight loss of more than 25% of body weight immediately after surgery is associated with an increased risk of gallstones. Dr. Lammert and his fellow researchers suggest that patients planning weight-loss surgery should talk to their doctors about taking ursodiol as a preventive measure. Ursodiol is actually a synthetic version of a bile acid that is already naturally found in the body, but, as with all drugs, side effects can sometimes occur. The most common are stomach upset, diarrhea, dizziness, back pain, hair loss and cough. Rare allergic reaction also can occur.

Because gallstones can form in as short a time as four weeks, ursodiol should be started within a few days after surgery. It can be stopped three to six months later. (Gallstone formation levels off about six months after the surgery.) Eating a higher proportion of fat is also helpful.

Of course, losing those extra pounds benefits health, but keep your doctor in the loop and consider working with a nutritionist or physician specializing in weight loss (such as an endocrinologist or bariatric physician) to help ensure that your weight-loss plan is effective and that you’re not putting yourself at risk for an attack of gallstones.