Gastric Surgery for Severe Obesity
Severe obesity is a chronic condition that is very difficult to treat.
Surgery to promote weight loss by restricting food intake or interrupting
digestive processes is an option for severely obese people. A body mass
index (BMI) above 40--which means about 100 pounds of overweight for men
and about 80 pounds for women--indicates that a person is severely obese
and therefore a candidate for surgery (see table 1). Surgery also may
be an option for people with a BMI between 35 and 40 who suffer from life-threatening
cardiopulmonary problems (for example, severe sleep apnea or obesity-related
heart disease) or diabetes. However, as in other treatments for obesity,
successful results depend mainly on motivation and behavior.
The Normal Digestive Process
Normally, as food moves along the digestive tract (see figure 1), appropriate
digestive juices and enzymes arrive at the right place at the right time
to 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 until eliminated.
How Does Surgery Promote Weight Loss?
The concept of gastric 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, produces
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 longer used.
Surgeons now use techniques that produce weight loss primarily by limiting
how much the stomach can hold. These restrictive procedures are often
combined with modified gastric bypass procedures that somewhat limit calorie
and nutrient absorption and may lead to altered food choices.
Two ways that surgical procedures promote weight loss are:
- By decreasing food intake (restriction). Gastric banding, gastric
bypass, and vertical-banded gastroplasty are surgeries that limit the
amount of food the stomach can hold by closing off or removing parts
of the stomach. These operations also delay emptying of the stomach
(gastric pouch).
- By causing food to be poorly digested and absorbed (malabsorption).
In the gastric bypass procedures, a surgeon makes a direct connection
from the stomach to a lower segment of the small intestine, bypassing
the duodenum, and some of the jejunum.
Although results of operations using these procedures are more predictable
and manageable, side effects persist for some patients.
What Are the Surgical Options?
Restriction Operations
Restriction operations are the surgeries most often used for producing
weight loss. Food intake is restricted by creating a small pouch at the
top of the stomach where the food enters from the esophagus. The pouch
initially holds about 1 ounce of food and expands to 2-3 ounces with time.
The pouch's lower outlet usually has a diameter of about 1/4 inch. The
small outlet delays the emptying of food from the pouch and causes a feeling
of fullness.
After an operation, the person usually can eat only a half to a whole
cup of food without discomfort or nausea. Also, food has to be well chewed.
For most people, the ability to eat a large amount of food at one time
is lost, but some patients do return to eating modest amounts of food
without feeling hungry.
Restriction operations for obesity include gastric banding and vertical
banded gastroplasty. Both operations serve only to restrict food intake.
They do not interfere with the normal digestive process.
- Gastric banding. In this procedure, a 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
(figure 2). In the future, it may be possible to perform gastric banding
with smaller incisions through a laparoscope, a flexible fiberoptic
tube and light source through which some surgical instruments may be
passed. Laparoscopic gastric banding has not yet been approved by the
Food and Drug Administration.
- Vertical banded gastroplasty (VBG). This procedure is
the most frequently used restrictive operation for weight control. As
figure 3 illustrates, both a band and staples are used to create a small
stomach pouch.
Restrictive operations lead to weight loss in almost all patients. However,
weight regain does occur in some patients. About 30 percent of persons
undergoing vertical banded gastroplasty achieve normal weight, and about
80 percent achieve some degree of weight loss. However, some patients
are unable to adjust their eating habits and fail to lose the desired
weight. In all weight-loss operations, successful results depend on your
motivation and behaviors.
A common risk of restrictive operations is vomiting caused by the small
stomach being overly stretched by food particles that have not been chewed
well. Other risks of VBG include erosion of the band, breakdown of the
staple line, and, in a small number of cases, leakage of stomach juices
into the abdomen. The latter requires an emergency operation. In a very
small number of cases (less than 1 percent) infection or death from complications
can occur.
Gastric Bypass Operations
These operations combine creation of small stomach pouches to restrict
food intake and construction of bypasses of the duodenum and other segments
of the small intestine to cause malabsorption.
- Roux-en-Y gastric bypass (RGB). This operation (figure
4) is the most common gastric bypass procedure. First, a small stomach
pouch is created by stapling or by vertical banding. This causes restriction
in food intake. Next, a Y-shaped section of the small intestine is attached
to the pouch to allow food to bypass the duodenum (the first segment
of the small intestine) as well as the first portion of the jejunum
(the second segment of the small intestine). This causes reduced calorie
and nutrient absorption.
- Extensive gastric bypass (biliopancreatic diversion). In
this more complicated gastric bypass operation (figure 5), portions
of the stomach are removed. The small pouch that remains is connected
directly to the final segment of the small intestine, thus completely
bypassing both the duodenum and jejunum. Although this procedure successfully
promotes weight loss, it is not widely used because of the high risk
for nutritional deficiencies.
Gastric bypass operations (figures 4 and 5) that cause malabsorption
and restrict food intake produce more weight loss than restriction operations
(figures 2 and 3) that only decrease food intake. Patients who have bypass
operations generally lose two-thirds of their excess weight within 2 years.
The risks for pouch stretching, band erosion, breakdown of staple lines,
and leakage of stomach contents into the abdomen are about the same for
gastric bypass as for vertical banded gastroplasty. However, because gastric
bypass operations cause food to skip the duodenum, where most iron and
calcium are absorbed, risks for nutritional deficiencies are higher in
these procedures. Anemia may result from malabsorption of vitamin B12
and iron in menstruating women, and decreased absorption of calcium may
bring on osteoporosis and metabolic bone disease. Patients are required
to take nutritional supplements that usually prevent these deficiencies.
Gastric bypass operations also may cause "dumping syndrome,"
whereby stomach contents move too rapidly through the small intestine.
Symptoms include nausea, weakness, sweating, faintness, and, occasionally,
diarrhea after eating, as well as the inability to eat sweets without
becoming so weak and sweaty that the patient must lie down until the symptoms
pass.
The more extensive the bypass operation, the greater is the risk for
complications and nutritional deficiencies. Patients with extensive bypasses
of the normal digestive process require not only close monitoring, but
also life-long use of special foods and medications.
Explore Benefits and Risks
Surgery to produce weight loss is a serious undertaking. Each individual
should clearly understand what the proposed operation involves. Patients
and physicians should carefully consider the following benefits and risks:
Benefits
- Immediately following surgery, most patients lose weight rapidly and
continue to do so until 18 to 24 months after the procedure. Although
most patients then start to regain some of their lost weight, few regain
it all.
- Surgery improves most obesity-related conditions. For example, in
one study blood sugar levels of most 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 had diabetes for a long time.
Risks
- Ten to 20 percent of patients who have weight-loss operations require
followup operations to correct complications. Abdominal hernias are
the most common complications requiring followup surgery. Less common
complications include breakdown of the staple line and stretched stomach
outlets.
- More than one-third of obese patients who have gastric 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 is increased. Gallstones can be prevented
with supplemental bile salts taken for the first 6 months after surgery.
- Nearly 30 percent of patients who have weight-loss surgery develop
nutritional deficiencies such as anemia, osteoporosis, and metabolic
bone disease. These deficiencies can be avoided if vitamin and mineral
intakes are maintained.
- Women of childbearing age should avoid pregnancy until their weight
becomes stable because rapid weight loss and nutritional deficiencies
can harm a developing fetus.
Is the Surgery for You?
For patients who remain severely obese after nonsurgical approaches to
weight loss have failed, or for patients who have an obesity-related disease,
surgery may be the best next step. But for other patients, greater efforts
toward weight control, such as changes in eating habits, behavior modification,
and increasing physical activity, may be more appropriate. Answers to
the following questions may help in your decision to undergo surgery for
weight loss.
Are you:
- unlikely to lose weight successfully with (further) nonsurgical measures?
- well informed about the surgical procedure and the effects of treatment?
- determined to lose weight and improve your health?
- aware of how your life may change after the operation (adjustment
to the side effects of the surgery, including need to chew well and
inability to eat large meals)?
- aware of the potential for serious complications, the associated dietary
restrictions, and the occasional failures?
- committed to lifelong medical followup?
Do you:
- have a BMI of 40 or more?
- have an obesity-related physical problem (such as body size that interferes
with employment, walking, or family function)?
- have high-risk obesity-related health problems (such as severe sleep
apnea or obesity-related heart disease)?
Remember: There are no guarantees for any method, including surgery,
to produce and maintain weight loss. Success is possible only with your
fullest cooperation and commitment to behavioral change and medical followup--and
this cooperation and commitment should be carried out for the rest of
your life.
Source:
NIH Publication No. 96-4006
April 1996
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