Gallstones, Weight and Obesity
What are Gallstones?
Gallstones are clusters of solid material
that form in the gallbladder. They are made mostly of cholesterol. Gallstones
slowly grow in size and number and may disrupt the flow of bile from the
gallbladder into the duct system.
Experts estimate that 16 to 22 million
people in the United States have gallstones—as many as one in every
12 Americans. In rare cases, gallstones can cause serious health problems.
Symptomatic gallstones (a minority) result in about 800,000 hospitalizations
and more than 500,000 operations each year in the U.S.
What Causes Gallstones?
According to researchers, gallstones may
form in one of three ways: when bile contains more cholesterol than it
can dissolve, when there is too much of certain proteins or other substance
in the bile that causes cholesterol to form hard crystals, or when the
gallbladder does not contract and empty its bile regularly.
Note: Gallstones are largely attributed
to the western diet, due to a low intake of dietary fibre and highly refined
foods. This leads to a reduction in bile acid levels, which are essential
for maintaining the solubility of cholesterol. Treatment is therefore
best aimed at reducing those factors that contribute to the formation
of gallstones.
Is Obesity a Risk Factor for Gallstones?
Obesity is a strong risk factor for gallstones,
especially among women. People who are obese are more likely to have gallstones
than people who are at a healthy weight. Body
Mass Index (BMI) can be used to measure obesity in adults. A BMI
of about 19-25 refers to a healthy weight, a BMI of about 25 to 30 refers
to overweight, and a BMI of 30 or higher refers to obese.
As BMI increases, the risk for developing
gallstones also rises. Studies have shown that risk may triple in women
who have a BMI greater than 32 compared to those with a BMI of 24 to 25.
Risk may increase sevenfold in women with a BMI greater than 45 compared
to those with a BMI less than 24.
Researchers have found that people who
are obese may produce high levels of cholesterol. This leads to the production
of bile containing more cholesterol than it can dissolve. When this happens,
gallstones can form. People who are obese may also have large gallbladders
that do not empty normally or completely. Some studies have shown that
men and women who carry fat around their midsections may be at a greater
risk for developing gallstones than those who carry fat around their hips
and thighs.
Too Rapid Weight Loss When Dieting is
a Risk Factor for Gallstones
Weight-loss dieting increases the risk
of developing gallstones. People who lose a large amount of weight quickly
are at greater risk than those who lose weight more slowly. Rapid weight
loss may also cause silent gallstones to become symptomatic. Studies have
shown that people who lose more than 3 pounds per week may have a greater
risk of developing gallstones than those who lose weight at slower rates.
A very low-calorie diet (VLCD) allows a
person who is obese to quickly lose a large amount of weight. VLCDs usually
provide about 800 calories or less per day in food or liquid form, and
are followed for 12 to 16 weeks under the supervision of a health care
provider. Studies have shown that 10 to 25 percent of people on a VLCD
developed gallstones. These gallstones were usually silent—they did
not produce any symptoms. About one-third of the dieters who developed
gallstones, however, did have symptoms and some of these required gallbladder
surgery.
Experts 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. Following
a diet too low in fat or going for long periods without eating (skipping
breakfast, for example), a common practice among dieters, may also decrease
gallbladder contractions. If the gallbladder does not contract often enough
to empty out the bile, gallstones may form.
Is Weight Cycling a Risk Factor for Gallstones?
Weight cycling, or losing and regaining
weight repeatedly, may increase the risk of developing gallstones. People
who weight cycle - especially with losses and gains of more than 10 pounds
- have a higher risk for gallstones than people who lose weight and maintain
their weight loss. In addition, the more weight a person loses and regains
during a cycle, the greater the risk of developing gallstones.
Is Weight Loss Surgery to Treat Obesity
a Risk Factor for Gallstones?
Gallstones are common among people who
undergo gastrointestinal surgery to lose weight, also called bariatric
surgery. Gastrointestinal surgery to reduce the size of the stomach or
bypass parts of the digestive system is a weight-loss method for people
who have a BMI above 40. Experts estimate that one-third of patients who
have bariatric surgery develop gallstones. The gallstones usually develop
in the first few months after surgery and are symptomatic.
How Can I Safely Lose Weight and Decrease
the Risk of Gallstones?
You can take several measures to decrease
the risk of developing gallstones during weight loss.
- Losing weight gradually, instead of
losing a large amount of weight quickly, lowers your risk. Experts recommend
losing 1 to 2 pounds per week.
- You can also decrease the risk of gallstones
associated with weight cycling by aiming for a modest weight loss that
you can maintain. Even a loss of 10 percent of body weight over a period
of 6 months or more can improve the health of an adult who is overweight
or obese.
- Your food choices can also affect your
gallstone risk. Experts recommend including some fat in your diet to
stimulate gallbladder contracting and emptying. However, no more than
30 percent of your total calories should come from fat.
- Studies have also shown that diets high
in fiber and calcium may reduce the risk of gallstone development.
- Finally, regular physical activity is
related to a lower risk for gallstones.
According to research, increased intake
of both soluble and insoluble fibre, which includes vegetables, nuts,
pectin has been found to decrease the formation of deoxycholic, which
increases the solubility of cholesterol, by promoting its excretion through
faeces.
A diet comprising of high fibre such as
found in a vegetarian diet has been shown to offer a protective factor
against gallstone formation.
Are the Benefits of Weight Loss Greater
Than the Risk of Gallstones?
Although weight loss can increase the risk
of developing gallstones, obesity poses an even greater risk. In addition
to gallstones, obesity is linked to many serious health problems including:
- Type 2 diabetes
- High blood pressure
- Heart disease
- Stroke
- Certain types of cancer
- Sleep apnea (when breathing stops for
short periods during sleep)
- Osteoarthritis (wearing away of the
joints)
- Gastro-esophageal reflux disease (GERD)
For people who are obese, weight loss can
lower the risk of developing these illnesses. Even a small weight loss
of 10 to 20 pounds can improve health and lower disease risk. In addition,
weight loss can bring other benefits such as better mood and positive
self-image.
Note: If you are thinking about starting
an eating and physical activity plan to lose weight, talk with your health
care provider first. Together, you can discuss various eating and exercise
programs, your medical history, and the benefits and risks of losing weight
including the risk of developing gallstones.
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Further Information on Gallstones:
Acalovschi M. “Cholesterol gallstones:
From epidemiology to prevention.” Postgraduate Medicine, 2001: Vol.
77, No. 906, pp. 221-229. This review article, intended for health professionals,
describes the causes, risk factors, and pathogenesis of gallstones, and
provides information on prevention.
Erlinger S. “Gallstones in obesity
and weight loss.” European Journal of Gastroenterology Hepatology,
2000: Vol. 12, No. 12, pp. 1347-1352. This review article, intended for
health professionals, describes the relationships of diet, weight reduction,
and obesity to the development of gallstones. It also describes the pathophysiology
of gallstones and recommendations for treatment and prevention.
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