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 silentgallstones. 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
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
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
According to researchers,
cholesterol gallstones may form in several
ways, such as:
When bile contains more cholesterol than it
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
When the gallbladder does not contract and
empty its bile regularly.
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. Obesity in adults can be
defined using the body mass index (BMI), a tool
that measures weight in relation to height. The
table below shows how the BMI calculation works.
A BMI of 18.5 to 24.9 refers to a healthy weight,
a BMI of 25 to 29.9 refers to overweight, and a
BMI of 30 or higher refers to obesity.
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
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
* Without Shoes
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 wheight.
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
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
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.
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 lbs-have a
higher risk for gallstones than people who lose
weight and sustain their weight loss. Additionally, the more weight a person loses and
regains during a cycle, the greater the risk of
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.
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.
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
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.
Silent gallstones are usually left alone and
sometimes disappear on their own. Symptomatic
gallstones are usually treated. The most common
treatment is surgery to remove the gallbladder.
This operation is called a
cholecystectomy. In other cases, drugs
are used to dissolve the gallstones. Your health
care professional can help determine which option is
best for you.
Although weight loss increases the risk of
developing gallstones, obesity poses an even
greater risk. In addition to gallstones, obesity
is linked to many serious health problems,
type 2 diabetes
high blood pressure
certain types of cancer
sleep apnea (when breathing stops for short
periods during sleep)
osteoarthritis (wearing away of the
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
If you are thinking about starting an eating and
physical activity plan 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.
Clinical Guidelines on the Identification,
Evaluation, and Treatment of Overweight and
Obesity in Adults: The Evidence Report.
National Institutes of Health (NIH) Publication
No. 98-4083. September 1998. This National Heart,
Lung, and Blood Institute report targets primary
care practitioners and provides evidence for the
effects of treatment on overweight and
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,
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.