What are
gallstones?Gallstones are clusters of solid material that form in the
gallbladder. The most common type is made mostly of cholesterol.
Gallstones may occur as one large stone or as many small ones. They
vary in size and may be as large as a golf ball or as small as a
grain of sand.
Experts estimate that 10 to 15 percent of
people in the United States have gallstones—as many as 42 million
Americans. Most people with gallstones do not know that they have
them and experience no symptoms. Painless gallstones are called
silent gallstones. Sometimes gallstones can cause
abdominal or back pain. These are called symptomatic
gallstones. In rare cases, gallstones can cause serious health
problems. Symptomatic gallstones result in about 800,000
hospitalizations and more than 500,000 operations each year in the
United States.
Gallstones develop in the
gallbladder, a small pear-shaped organ located beneath the liver on
the right side of the abdomen. The gallbladder is about 3 inches
long and 1 inch wide at its thickest part. It stores and releases
bile into the intestine to help digestion.
Bile is a liquid made by the liver. It contains water, cholesterol, bile salts, fats, proteins, and bilirubin (a bile pigment). During digestion, the gallbladder contracts to release bile into the intestine, where the bile salts help to break down fat. Bile also dissolves excess cholesterol.
According to researchers, cholesterol gallstones may form in several ways, such as:
- When bile contains more cholesterol than it can dissolve.
- When there is too much bilirubin or other substance in the
bile that causes cholesterol to form hard crystals.
- When there are not enough bile salts to break down fat.
- When the gallbladder does not contract and empty its bile regularly.
Some common symptoms of gallstones or gallstone attack include:
- Severe pain in the upper abdomen that starts suddenly and lasts from 30 minutes to many hours.
- Pain under the right shoulder or in the right shoulder blade.
- Nausea or vomiting.
- Indigestion after eating high-fat foods, such as fried foods or desserts.
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. The risk may be seven times higher in women with a BMI above 45 than in those with a BMI below 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.
Table 1. Body Mass Index
* Without Shoes
**Without
Clothes
Sources
George Bray, M.D., Pennington Biomedical Research Center.
National Heart, Lung, and Blood Institute’s Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The Evidence Report.
Find your weight on the bottom of the graph. Go straight up from that point until you come to the line that matches your height. Then look to find your weight group.
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 lbs 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 per day in food or liquid form, and are
followed for 12 to 16 weeks under the supervision of a health care
professional. 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 weight-loss 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.
A drug called ursodiol that helps
dissolve cholesterol in the bile may help prevent gallstones from
developing during rapid weight loss. While ursodiol is not approved
by the Food and Drug Administration (FDA) to prevent gallstones, its
“off-label” use (the practice of prescribing medications for periods
of time or for conditions not FDA-approved) has been shown to be
effective and safe. If rapid weight loss is highly likely, you
should consider talking with your health care provider about using
ursodiol.
Why weight cycling is a risk factor for gallstones is unclear. The rise in cholesterol levels during the weight-loss phase of a weight cycle may be responsible. It is also thought that each cycle increases one’s risk for gallstones. However, further research is required to determine the exact link between weight loss and the risk 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. This procedure is also an option for people who have a BMI above 35 with comorbid conditions such as diabetes and high blood pressure. Experts estimate that about one-third of patients who have bariatric surgery develop gallstones. The gallstones usually develop in the first few months after surgery and are symptomatic.
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. Depending on your starting weight, experts recommend losing weight at the rate of 1/2 to 2 lbs per week. Losing weight at this rate commonly occurs for up to 6 months. After 6 months, weight loss usually declines and weight stabilizes because individuals in lower weight groups use fewer calories (energy). 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 5 to 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. Current recommendations indicate that 20 to 35 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. Aim for approximately 60 minutes of moderate- to vigorous-intensity activity on most days of the week to manage your body weight and prevent unhealthy weight gain. To sustain weight loss, engage in at least 60 to 90 minutes of daily moderate-intensity physical activity.
- 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)
- fatty liver disease
For people who are obese, weight loss can lower the
risk of developing some of these illnesses. A small weight loss of
10 percent of body weight over a period of 6 months may improve
health and lower disease risk. In addition, weight loss may bring
other benefits such as better mood, increased energy, and positive
self-image.
If you are thinking about starting an eating and
physical activity
weight loss program
to lose weight, talk with your health care
professional first. Together, you can discuss various eating and
physical activity programs, your medical history, and the benefits
and risks of losing weight, including the risk of developing
gallstones.
Finding Your Way to a Healthier You: Based on the “Dietary Guidelines for Americans.” U.S. Department of Health and Human Services (DHHS) Publication No. HHS-ODPHP-2005-01-DGA-B. 2005. This brochure from the DHHS and the U.S. Department of Agriculture provides basic guidelines for eating a healthy diet and being physically active.
Gallstones. NIH Publication No. 05-2897. November 2004. This fact sheet provides basic information about gallstones and treatment options. Published by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and available through the National Digestive Diseases Information Clearinghouse, 2 Information Way, Bethesda, MD, 20892-3570, toll-free number: 1-800-891-5389.
Gastrointestinal Surgery for Severe Obesity. NIH Publication No. 04-4006. December 2004. This fact sheet provides basic information about bariatric surgery, including benefits and risks. Published by NIDDK and available through the Weight-control Information Network (WIN), 1 WIN Way, Bethesda, MD, 20892-3665, toll-free number: 1-877-946-4627.
Prescription Medications for the Treatment of Obesity. NIH Publication No. 04-4191. November 2004. Information, including potential benefits and side-effects of current FDA-approved prescription weight-loss medications, is provided in this fact sheet. Published by NIDDK and available through WIN.
Weight Cycling. NIH Publication No. 01-3901. August 2001. This fact sheet provides general information about weight cycling and associated health risks. Published by NIDDK and available through WIN.
Weight Loss for Life. Information about healthful weight loss as well as weight-loss program options is provided in this brochure. NIH Publication No. 04-3700. June 2004. Published by NIDDK and available through WIN.
Weight-control Information Network
1 WIN WAY
BETHESDA, MD 20892-3665
Phone: (202) 828-1025
Toll-free number: 1-877-946-4627
FAX: (202) 828-1028
Email: WIN@info.niddk.nih.gov
The Weight-control Information Network (WIN) is a national information service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) of the National Institutes of Health (NIH), which is the Federal Government’s lead agency responsible for biomedical research on nutrition and obesity. Authorized by Congress (Public Law 103-43), WIN provides the general public, health professionals, the media, and Congress with up-to-date, science-based health information on weight control, obesity, physical activity, and related nutritional issues. Publications produced by WIN are reviewed by both NIDDK scientists and outside experts. This fact sheet was also reviewed by Jay Everhart, M.D., M.P.H., Chief, Epidemiology and Clinical Trials Branch, NIDDK; Van S. Hubbard, M.D., Ph.D., CAPT, USPHS, Director, Division of Nutrition Research Coordination, NIH; and Susan Z. Yanovski, M.D., Director, Obesity and Eating Disorders Program and Co-Director, Office of Obesity Research, NIDDK.
This publication is not copyrighted. WIN encourages users of this fact sheet to duplicate and distribute as many copies as desired.
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
National
Institutes of Health
NIH Publication No. 02-3677
February 2002
Updated April
2006
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