More than 15 million Americans have a BMI -- body mass index -- of 40 or more and are considered morbidly obese, according to the Society of American Gastrointestinal and Endoscopic Surgeons. Unfortunately, a program of diet, behavior modification, medication and exercise rarely achieves long-term weight loss. In fact, the rate of weight loss loss without surgery averages only four percent. Weight loss surgery, include gastric bypass, helps morbidly obese patients lose weight and keep it off.
Process
Some weight loss or bariatric surgery procedures help with weight loss by restricting the size of the patient's stomach. Restrictive procedures, included adjustable gastric banding and vertical gastric sleeve, make the patient feel full sooner, according to the National Institutes of Health. Gastric bypass surgery restricts the size of the stomach by creating a small pouch and removing the remainder of the stomach. It also reroutes the digestive system, bypassing part of the intestine and blocking some calorie absorption.
Because the gastric bypass combines both a restrictive element and a malabsorption element, total weight loss tends to be higher than with a purely restrictive procedure. However, patients risk nutrient deficiencies and dumping syndrome -- nausea, vomiting, diarrhea and abdominal discomfort -- when they eat too much sugar or fat.
Qualifications
A patient desiring gastric bypass surgery must meet several qualifications before being approved, according to the National Institutes of Health. First, her BMI -- body mass index -- must be at least 40. The BMI, calculated on the basis of height and weight, indicates the degree of obesity. A person with a BMI of 40 would be approximately 100 lbs overweight. A patient who has a BMI of 35 or more may qualify if she has one or more obesity-related diseases, such as high blood pressure, sleep apnea or diabetes. Second, the patient must be in good enough health to withstand surgery and free of psychiatric or substance abuse issues that would tend to sabotage the surgery. Third, the health care insurance provider, the surgeon or both may require her to lose a certain amount of weight before surgery.
Purpose
Preoperative diets before gastric bypass surgery may serve one or more purposes. First, a very low calorie diet before surgery shrinks the size of the liver by about 20 percent, says the American Society of Metabolic and Bariatric Surgeons. When the surgeon uses the laparoscopic approach to gastric bypass, performing the procedure through several small incisions with special instruments and a tiny video camera, reducing the liver size improves access to the upper stomach.
Second, patients who lose 10 percent of their excess weight prior to surgery tend to lose weight more rapidly after surgery. Third, limiting the patient to clear liquids a few days before the procedure and helps to clear the bowel, reducing the risk of infection. Finally, patients covered by certain health care insurance plans must undergo a mandatory physician-supervised diet program before the carrier will approve them for surgery.
Misconceptions
Although preoperative liquid diets effectively shrink the liver, reduce weight and help to clear the bowels, no conclusive evidence exists for the clinical benefits of undergoing a six-month medically supervised weight loss program prior to gastric bypass, according to the American Society of Metabolic and Bariatric Surgeons.
In a study comparing weight loss between a group of patients who underwent two months of diet counseling versus those who participated in an insurance-carrier mandated medically supervised weight loss plan for six months, no significant difference was noted between the groups. According to Timothy Kuwada, MD, the study's lead investigator, little difference in pre- and post-operative weight loss was found. The only significant difference was that one group had to wait an extra four months before the procedure was approved.
Foods Permitted on Diets
Preoperative diets consist of various guidelines, depending on the bariatric surgeon's guidelines. Some patients undergo a two-week clear liquid diet with bowel prep, including enemas. Others drink full liquids -- any food that is liquid at room temperature for four weeks, then clear liquids for two weeks. Those undergoing medically managed six-month programs may eat a low-calorie diet or consume meal replacement shakes according to the surgeon's guidelines.
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