Dieting and Gallstones

As most people know, there are significant health benefits to be gained from losing excess kgs, for example, many people can reduce high blood pressure and cholesterol levels through weight loss. Overweight people are at greater risk of developing gallstones than people of average weight. However, people who are considering a diet program requiring very low intake of calories each day should be aware that during rapid or substantial weight loss, a person’s risk of developing gallstones is increased.

What are gallstones?

Gallstones are clumps of solid material that form in the gallbladder. They may occur as a single, large stone or many small stones. Gallstones are a mixture of compounds, but typically they are mostly cholesterol.  One in
ten Australians has gallstones. However, most people with gallstones don’t know they have them and experience no symptoms. Painless gallstones are called silent gallstones. For an unfortunate minority, however,
gallstones can cause painful attacks. Painful gallstones are called symptomatic gallstones, because they cause symptoms. In rare cases gallstones can cause life-threatening complications. Symptomatic gallstones result
in 100′s of thousands of hospitalisations and operations each year.

What Causes Gallstones?

Gallstones develop in the gallbladder, a pear-shaped organ beneath the liver on the right side of the abdomen. It’s about 3 inches long and an inch wide at its thickest part. The gallbladder stores and releases bile into the intestine to aid digestion. 

Bile is a fluid made by the liver that helps in digestion. Bile contains substances called bile salts that act like natural detergents to break down fats in the food we eat. As food passes from the stomach into the small intestine, the gallbladder releases bile into the bile ducts. These ducts, or tubes, run from the liver to the intestine. Bile also helps eliminate excess cholesterol from the body. The liver secretes cholesterol into the bile, which is then eliminated from the body via the digestive system.

Most researchers believe three conditions are necessary to form gallstones. First, the bile becomes supersaturated with cholesterol, which means the bile contains more cholesterol than the bile salts can dissolve. Second, an imbalance of proteins or other substances in the bile causes the cholesterol to start to crystallise. Third, the gallbladder does not contract enough to empty its bile regularly.

Are Obese People More Likely To Develop Gallstones?

 Yes. Obesity is a strong risk factor for gallstones.   Scientists often use a mathematical formula called body mass index (BMI) to define obesity. (BMI = weight in kilograms divided by height in meters squared. The more obese a person is, the greater his or her risk is of developing gallstones. 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.

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 4 to 10 Kg (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 10Kg 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 repeateddieting on gallstone formation.

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