Things You Should Know About Gastric Bypass Surgery
From the Weight-Control Information Network
Severe obesity is a chronic condition that is
difficult to treat through diet and exercise
alone. Gastrointestinal surgery is the best option
for people who are severely obese and cannot
lose weight by traditional means or who suffer
from serious obesity-related health problems.
The surgery promotes weight loss by restricting
food intake and, in some operations, interrupting
the digestive process. As in other treatments
for obesity, the best results are achieved with
healthy eating behaviors and regular physical
People who may consider gastrointestinal surgery
include those with a body mass index (BMI) above
40—about 100 pounds of overweight for men
and 80 pounds for women. People with a BMI between
35 and 40 who suffer from type 2 diabetes or
life-threatening cardiopulmonary problems such
as severe sleep apnea or obesity-related heart
disease may also be candidates for surgery.
The concept of gastrointestinal surgery to control
obesity grew out of results of operations for
cancer or severe ulcers that removed large portions
of the stomach or small intestine. Because patients
undergoing these procedures tended to lose weight
after surgery, some physicians began to use such
operations to treat severe obesity.
The first operation that was widely used for
severe obesity was the intestinal bypass. This
operation, first used 40 years ago, produced
weight loss by causing malabsorption. The idea
was that patients could eat large amounts of
food, which would be poorly digested or passed
along too fast for the body to absorb many calories.
The problem with this surgery was that it caused
a loss of essential nutrients and its side effects
were unpredictable and sometimes fatal. The original
form of the intestinal bypass operation is no
The Normal Digestive Process
Normally, as food moves along the digestive tract,
digestive juices and enzymes digest and absorb
calories and nutrients. After we chew and swallow
our food, it moves down the esophagus to the
stomach, where a strong acid continues the digestive
process. The stomach can hold about 3 pints of
food at one time. When the stomach contents move
to the duodenum, the first segment of the small
intestine, bile and pancreatic juice speed up
digestion. Most of the iron and calcium in the
foods we eat is absorbed in the duodenum. The
jejunum and ileum, the remaining two segments
of the nearly 20 feet of small intestine, complete
the absorption of almost all calories and nutrients.
The food particles that cannot be digested in
the small intestine are stored in the large intestine
How Does Surgery Promote Weight Loss?
Gastrointestinal surgery for obesity, also called
bariatric surgery, alters the digestive process.
The operations promote weight loss by closing
off parts of the stomach to make it smaller.
Operations that only reduce stomach size are
known as “restrictive operations” because
they restrict the amount of food the stomach
Some operations combine stomach restriction with
a partial bypass of the small intestine. These
procedures create a direct connection from the
stomach to the lower segment of the small intestine,
literally bypassing portions of the digestive
tract that absorb calories and nutrients. These
are known as malabsorptive operations.
the Surgical Options?
There are several types of restrictive and malabsorptive
operations. Each one carries its own benefits
Restrictive operations serve only to restrict
food intake and do not interfere with the normal
digestive process. To perform the surgery, doctors
create a small pouch at the top of the stomach
where food enters from the esophagus. Initially,
the pouch holds about 1 ounce of food and later
expands to 2-3 ounces. The lower outlet of the
pouch usually has a diameter of only about _
inch. This small outlet delays the emptying of
food from the pouch and causes a feeling of fullness.
As a result of this surgery, most people lose
the ability to eat large amounts of food at one
time. After an operation, the person usually
can eat only about 1 cup of food without discomfort
or nausea. Also, food has to be well chewed.
Restrictive operations for obesity include adjustable
gastric banding (AGB) and vertical banded gastroplasty
Adjustable gastric banding. In this procedure,
a hollow band made of special material is placed
around the stomach near its upper end, creating
a small pouch and a narrow passage into the larger
remainder of the stomach. The band is then inflated
with a salt solution. It can be tightened or
loosened over time to change the size of the
passage by increasing or decreasing the amount
of salt solution.
Vertical banded gastroplasty. VBG has been the
most common restrictive operation for weight
control. Both a band and staples are used to
create a small stomach pouch.
Although restrictive operations lead to weight
loss in almost all patients, they are less successful
than malabsorptive operations in achieving substantial,
long-term weight loss. About 30 percent of those
who undergo VBG achieve normal weight, and about
80 percent achieve some degree of weight loss.
Some patients regain weight. Others are unable
to adjust their eating habits and fail to lose
the desired weight. Successful results depend
on the patient’s willingness to adopt a
long-term plan of healthy eating and regular
A common risk of restrictive operations is vomiting,
which is caused when the small stomach is overly
stretched by food particles that have not been
chewed well. Band slippage and saline leakage
have been reported after AGB. Risks of VBG include
wearing away of the band and breakdown of the
staple line. In a small number of cases, stomach
juices may leak into the abdomen, requiring an
emergency operation. In less than 1 percent of
all cases, infection or death from complications
Malabsorptive operations are the most common
gastrointestinal surgeries for weight loss. They
restrict both food intake and the amount of calories
and nutrients the body absorbs.
Roux-en-Y gastric bypass (RGB). This operation
is the most common and successful malabsorptive
surgery. First, a small stomach pouch is created
to restrict food intake. Next, a Y-shaped section
of the small intestine is attached to the pouch
to allow food to bypass the lower stomach, the
duodenum (the first segment of the small intestine),
and the first portion of the jejunum (the second
segment of the small intestine). This bypass
reduces the amount of calories and nutrients
the body absorbs.
Biliopancreatic diversion (BPD). In this more
complicated malabsorptive operation, portions
of the stomach are removed. The small pouch that
remains is connected directly to the final segment
of the small intestine, completely bypassing
the duodenum and the jejunum. Although this procedure
successfully promotes weight loss, it is less
frequently used than other types of surgery because
of the high risk for nutritional deficiencies.
A variation of BPD includes a “duodenal
switch” (see figure 6), which leaves a
larger portion of the stomach intact, including
the pyloric valve that regulates the release
of stomach contents into the small intestine.
It also keeps a small part of the duodenum in
the digestive pathway.
Malabsorptive operations produce more weight
loss than restrictive operations, and are more
effective in reversing the health problems associated
with severe obesity. Patients who have malabsorptive
operations generally lose two-thirds of their
excess weight within 2 years.
In addition to the risks of restrictive surgeries,
malabsorptive operations also carry greater risk
for nutritional deficiencies. This is because
the procedure causes food to bypass the duodenum
and jejunum, where most iron and calcium are
absorbed. Menstruating women may develop anemia
because not enough vitamin B12 and iron are absorbed.
Decreased absorption of calcium may also bring
on osteoporosis and metabolic bone disease. Patients
are required to take nutritional supplements
that usually prevent these deficiencies. Patients
who have the biliopancreatic diversion surgery
must also take fat-soluble (dissolved by fat)
vitamins A, D, E, and K supplements.
RGB and BPD operations may also cause “dumping
syndrome.” This means that stomach contents
move too rapidly through the small intestine.
Symptoms include nausea, weakness, sweating,
faintness, and sometimes diarrhea after eating.
Because the duodenal switch operation keeps the
pyloric valve intact, it may reduce the likelihood
of dumping syndrome.
The more extensive the bypass, the greater the
risk for complications and nutritional deficiencies.
Patients with extensive bypasses of the normal
digestive process require close monitoring and
life-long use of special foods, supplements,
Explore Benefits and Risks
Surgery to produce weight loss is a serious undertaking.
Anyone thinking about surgery should understand
what the operation involves. Patients and physicians
should carefully consider the following benefits
Right after surgery, most patients lose weight
quickly and continue to lose for 18 to 24 months
after the procedure. Although most patients regain
5 to 10 percent of the weight they lost, many
maintain a long-term weight loss of about 100
Surgery improves most obesity-related conditions.
For example, in one study, blood sugar levels
of 83 percent of obese patients with diabetes
returned to normal after surgery. Nearly all
patients whose blood sugar levels did not return
to normal were older or had lived with diabetes
for a long time.
Ten to twenty percent of patients who have weight-loss
surgery require follow-up operations to correct
complications. Abdominal hernia was the most
common complication requiring follow-up surgery,
but laparoscopic techniques seem to have solved
this problem. In laparoscopy, the surgeon makes
one or more small incisions through which slender
surgical instruments are passed. This technique
eliminates the need for a large incision and
creates less tissue damage. Patients who are
super obese (>350 pounds) or have had previous
abdominal surgery may not be good candidates
for laparoscopy, however. Less common complications
include breakdown of the staple line and stretched
Some obese patients who have weight-loss surgery
develop gallstones. Gallstones are clumps of
cholesterol and other matter that form in the
gallbladder. During rapid or substantial weight
loss, a person’s risk of developing gallstones
increases. Taking supplemental bile salts for
the first 6 months after surgery can prevent
Nearly 30 percent of patients who have weight-loss
surgery develop nutritional deficiencies such
as anemia, osteoporosis, and metabolic bone disease.
These deficiencies usually can be avoided if
vitamin and mineral intakes are high enough.
Women of childbearing age should avoid pregnancy
until their weight becomes stable because rapid
weight loss and nutritional deficiencies can
harm a developing fetus.
Gastrointestinal surgery costs about $15,000.
Medical insurance coverage varies by state and
insurance provider. If you are considering gastrointestinal
surgery, contact your regional Medicare or Medicaid
office or insurance plan to find out if the procedure
Is the Surgery for You?
Gastrointestinal surgery may be the next step
for people who remain severely obese after trying
non-surgical approaches, or for people who have
an obesity-related disease. Candidates for surgery
- A BMI of 40 or more
- A life-threatening obesity-related
health problem such as diabetes, severe sleep
apnea, or heart
disease and a BMI of 35 or more
- Obesity-related physical
problems that interfere with employment,
or family function.
If you fit the profile for
surgery, answers to the following questions
may help you
weight-loss surgery is appropriate
to lose weight successfully
with non-surgical measures?
- Well-informed about the
surgical procedure and the effects
- Determined to lose weight
and improve your health?
- Aware of how your life
may change after the
the surgery, including
the need to chew well
and inability to eat
- Aware of the potential
for serious complications,
and occasional failures?
- Committed to lifelong
Remember: There are no guarantees
Success is possible only
change and medical follow-up—and
this cooperation and commitment must
out for the rest of your
The Weight-control Information
is a service of the National
Diseases of the National
Health, which is
responsible for biomedical
on nutrition and obesity.
Law 103-43), WIN provides
general public, health
professionals, the media,
information on weight
and related nutritional