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Obesity
is becoming a major health problem in the United States. Today, more than 1
in every 3 people in the United States is obese. Obese patients are at increased
risk of developing illnesses as well as death. Morbidly obese patients have
been shown to have a 12 times reduction in life expectancy. Obesity is measured
in terms of a person's Body Mass Index (BMI), which is calculated from a person's
height and weight. A normal person would have a BMI between 20 and 25. Morbid
obesity is defined as a BMI of over 40, and usually correlates to actual body
weight exceeding ideal body weight by 100 lbs (45.5 kg). Anatomy
and Physiology
- In order
to understand how bariatric surgery results in weight loss, it is necessary
to understand how food is digested (Figure 1)
- After
swallowing, food enters the stomach, which acts to hold the food and then
allow small amounts of the food to pass further into the digestive tract.
The volume of the stomach is usually between 600 - 1000 cc (20 - 30 oz.)
- In
the first part of the small bowel (duodenum), food comes into contact
with bile, secreted by the liver as well as enzymes from the pancreas.
These secretions help in the digestion and absorption of food. The small
bowel is where most of the absorption of food occurs and may reach a length
of 6 - 7 meters (over 20 feet). The proximal (closest to the mouth) two-fifths
of the small bowel is called the jejunum and the distal (farthest from
the mouth) three-fifths is called the ileum
- Most
bariatric procedures work by two methods - a restrictive component and a malabsorptive
component
- Restrictive
component - a portion of the stomach may be removed or bypassed so as
to reduce the volume of the stomach. Thus, only a limited amount of food
can be eaten prior to getting full
- Malabsorptive
component - Bile and pancreatic secretions, which are necessary for digestion
of food, are directed away from the food. These secretions reach the food
several yards down the length of the small bowel, thus delaying and causing
incomplete digestion and absorption of the food
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| Figure
1 - Anatomy of the gastrointestinal (stomach and bowel) tract. Note that
digestive juices from the pancreas and liver enter the small bowel at the
duodenum. The proximal 2/5 of the small bowel is called the jejunum. The
distal 3/5 is called the ileum. The small bowel empties into the colon (large
bowel). © S. Brett |
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