Bariatrics is the field of medicine devoted to the treatment of overweight and obesity. Bariatric surgery, also known as weight loss surgery or as gastric bypass surgery, is the medical term for surgical procedures designed to produce weight loss.
Bariatric surgery is typically reserved for people who have a BMI of 40 or greater. This translates into one hundred pounds or more of excess weight on a man and 80 or more pounds of excess weight on a woman. Bariatric surgery may be appropriate for people who have somewhat less weight to lose if they have significant health problems like diabetes, heart disease and/ or sleep apnea.
A variety of different surgical procedures designed to produce weight loss have been developed over the past thirty years. The goal of all of these procedures has been to dramatically reduce the amount of calories people are able to obtain from their food, thus ensuring significant weight loss. This may be achieved by reducing the amount of food a person can eat, decreasing nutrient digestion and absorption, or a combination of both tactics.
Most people who have bariatric surgery lose a lot of weight rather quickly, especially if they have a combined procedure (one that reduces both food intake and digestion/absorption). People are able to keep most of the weight off if they follow diet and exercise guidelines for the remainder of their lives.
Purely restrictive operations significantly limit food intake but do not interfere with digestion and absorption. Purely restrictive operations include vertical banding (more properly known as vertical banded gastroplasty or VGB), adjustable gastric banding (AGB) such as the lap-band, and the sleeve gastrectomy. Following a restrictive surgery, the stomach pouch is roughly the size of a walnut in its shell and can only hold about an ounce of food. Over time, it can stretch to hold 2-3 ounces.
The key advantages of restrictive procedures are that they are easier to perform and therefore, patients are less prone to complications than patients who elect to undergo malabsorptive or combined procedures. Restrictive procedures also tend to be safer than malabsorptive procedures. However, purely restrictive procedures do not usually produce as much weight loss and people who have purely restrictive procedures have more trouble maintaining their weight loss in the long term.
Vertical Banded Gastroplasty
This procedure uses a band placed around the top of the stomach and staples to create a small pouch at the top of the stomach. At one time, it was the most common restrictive procedure performed, but it has fallen out of favor in recent years as Adjustable Gastric Band has gained popularity with doctors and their patients.
Adjustable Gastric Band
During this laparoscopic procedure, surgeons place a hollow silicone ring (a lap-band) around the top of the stomach to create a small pouch. The ring is connected via thin silicon tubing to a small injection port that is located directly under the skin of the abdomen. The degree of food restriction can be adjusted by pumping sterile saline into or removing it from the hollow ring with a fine-tipped needle. AGB is the only form of bariatric surgery that is reversible.
This is the newest bariatric surgery procedure. During this procedure, a surgeon staples off the rear pouch-shaped portion of the stomach, leaving just a slender sleeve-shaped tube to connect the esophagus at the top of the stomach and the duodenum (the first part of the small intestine) at the bottom end. Sleeve gastrectomies are usually performed as the first step in a series of baratric surgeries for very obese individuals.
Purely Malabsorptive Procedures
Purely malabsorptive procedures that bypass large sections of the intestine are no longer performed because they caused significant side effects including potentially dangerous nutritional deficiencies, electrolyte imbalances, and dehydration. These types of surgeries are now performed only in combination with restrictive procedures and patients electing this type of combination are carefully monitored for these side effects.
The combined procedure that blends restrictive and malabsorptive techniques is the most popular and most common option available today. These two combined procedures, the Roux-en-Y (RGB) and the Billiopancreatic Diversion (BPD), result in less food intake and less digestion/absorption of nutrients.
With the Roux-en-Y gastric bypass, many patients maintain a weight loss of 60-70% of their excess weight for 10 years or more. With BPD, most studies report an average loss of 75 to 80 percent of excess weight. Because combined operations result in greater weight loss than restrictive operations, they may also be more effective in improving the health problems associated with severe obesity such as hypertension (high blood pressure), sleep apnea, type 2 diabetes, and osteoarthritis.
Roux-en-Y Gastric Bypass
According to the National Institutes of Health, RGB is the most common and successful combined bariatric surgical procedure performed in the US. The first step is to staple off part of the stomach, creating a small pouch, to restrict food intake. The second half of the operation involves splitting the small intestine into a Y-shaped tube and connecting one arm of the Y to the new stomach pouch and the other arm of the Y to the jejunum (the middle portion of the small intestine). In bypassing the lower portion of the stomach and the first part of the small intestine (the duodenum), the procedure reduces the amount of food a person can digest and the nutrients/calories they can absorb.
This surgery is more complicated than the Roux-en-Y. It involves removing the lower portion of the stomach. The small pouch-shaped stomach that remains is connected to the illium, the last segment of the small intestine. Bypassing the first two segments of the small intestine (the duodenum and jejunum) creates significant and rapid weight loss, but it also puts patients at risk for significant nutritional deficiencies.