Assignment
Case Study: Nutrition & Metabolism
Worldwide, the incidence of obesity, defined as have too much body fat, has more than doubled since 1980. The United States has the largest rate of obesity with nearly 36% of American being obese. Obese is defined as having a body mass index greater than or equal to 30. Obesity greatly increases risks for a number of diseases such as type 2 Diabetes Mellitus, cardiovascular diseases, bone and joint issues, and even some cancers. Many obese patients struggle with weight loss using diet and exercise. For many of these patients, bariatric surgery can assist with the weight loss process.
There are 4 main types of bariatric surgery. Download docx above to see pictures.
Laparoscopic Adjustable Gastric Band (LAGB or lap-band)
In what is called a lap-band (laparoscopic adjustable gastric banding or LAGB) surgery, a silicone band is placed around the upper part of the stomach. Squeezed by the silicone band, the stomach becomes a pouch with about an inch-wide outlet. After banding, the stomach can only hold about an ounce of food. No removal of GI tissue or re-routing of the GI tract happens in this procedure. This procedure has the least side effects, but also is associated with less weight loss.
Gastric By-Pass
The most common form of weight loss surgery is the gastric by-pass (Roux-en-Y or RYGB). In gastric bypass, the stomach is made smaller by surgically creating a small pouch of the top of the stomach and separating the rest of the stomach into a larger pouch not connected to the esophagus. The smaller stomach is connected directly to the middle portion of the small intestine, bypassing the rest of the stomach and the upper portion of the small intestine. The upper portion of the small intestine is then connected to the upper part of the small intestine.
Sleeve Gastrectomy
The laparoscopic sleeve gastrectomy, often called the sleeve, is performed by removing approximately 80 percent of the stomach. The remaining stomach is a tubular pouch that resembles a banana.
Biliopancreatic Diversion with duodenal switch (BPD/DS)
The Biliopancreatic Diversion with Duodenal Switch (BPD/DS) is a procedure with two components. First, a smaller, tubular stomach pouch is created by removing a portion of the stomach, very similar to the sleeve gastrectomy. Next, a large portion of the small intestine is bypassed. The duodenum, or the first portion of the small intestine, is divided just past the outlet of the stomach. A segment of the distal (last portion) small intestine is then brought up and connected to the outlet of the newly created stomach, so that when the patient eats, the food goes through a newly created tubular stomach pouch and empties directly into the last segment of the small intestine. Roughly three-fourths of the small intestine is bypassed by the food stream.
The bypassed small intestine, which carries the bile and pancreatic enzymes that are necessary for the breakdown and absorption of protein and fat, is reconnected to the last portion of the small intestine so that they can eventually mix with the food stream. Similar to the other surgeries described above, the BPD/DS initially helps to reduce the amount of food that is consumed; however, over time this effect lessens and patients are able to eventually consume near "normal" amounts of food. Unlike the other procedures, there is a significant amount of small bowel that is bypassed by the food stream.
I. Describe the basic mechanism by which the lap-band (LAGB) surgery assists in weight loss.
II. What changes in nutritional needs would you expect with a gastric bypass (RYGB) surgery that are different from what you would see with a lap-band (LAGB) surgery?
III. A particular vitamin deficiency is common in patients that have had a gastric bypass (RYGB). Which vitamin would you most worry about and why? Why would the deficiency be more pronounced in this surgery than lap-band (LAGB)?
IV. What gut appetite signaling hormone would you expect to be reduced with any procedure that resects the greater curvature of the stomach (like the sleeve gastrectomy and BPD/DS)? What effect would this have on the patient's satiety?
V. Compare and contrast the effects of Lap-band (LAGB) vs BPD/DS on protein digestion and absorption.
VI. How would a decrease in caloric intake alter metabolism: Would blood glucose levels be high, low or normal? Would glycogen stores be built or degraded, ditto with fat stores and proteins? Does the metabolic rate change?