Question

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.

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.

1.Compare and contrast the effects of Lap-band (LAGB) vs BPD/DS on protein digestion and absorption.

2.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?

Answer 1

1. Effect of lap bad surgery

Due to restriction of dietary intake and/or malabsorption of dietary protein, bariatric surgery puts patients at risk for protein malnutrition. Protein is an important macronutrient for bariatric patients because it provides energy and also promotes wound healing and muscle protein synthesis. After bariatric surgery, protein intake is compromised because of reduced gastric capacity and aversion for certain foods. A few patients reach the recommended protein intake of 60 grams per day, which results in the loss of fat-free mass. Despite inadequate protein intake, protein digestion and absorption do not seem to be impaired suggesting that other mechanisms could counteract the reduced secretion of digestive enzymes and their delayed inlet.

In BPD surgery

Intake of protein during the immediate postoperative period is necessary to prevent the loss of lean body mass and maintain a positive nitrogen balance. Studies have shown that BPD patients have a  loss of endogenous nitrogen by a mean of 4.9 g/day. This leads to significant protein deficeincy in BPD patients.

2. Low blood sugar does not present until 2 to 3 years after gastric bypass surgery. These occur 2 to 3 hours after a meal. Fasting hypoglycemia is typically not seen. The etiology seems to be excessive insulin secretion in response to the meal. This is because people are more insulin sensitive after this surgery.

Glycogen storage is increased

Fat storage is decreased as it increases fat metabolism of stored fats

there is increased protein metabolism following gastric bypass surgery to make up for the loss of proteins following surgery

There is an overall increase in metabolism following gastric bypass surgery