Dr John P Wright
Updated: 9 October 2005
Last month the role of medication in the management of body weight was discussed. The ongoing television campaigns promising viewers weight reduction without calorie reduction continue to lore those who believe in ‘medical myths”. This unregulated marketing undermines the scientific evidence based medicine our readers aspire to.
The two areas to be discussed in this article are the role of surgery in the management of obesity, bariatric surgery, and the management of insulin resistance as a pre-diabetic condition or syndrome X.
Surgery for obesity is driven by the apparent hopelessness of the morbidly obese, those with a Body Mass Index (BMI ) = 40 kg/m2. BMI is defined as body weight in kilograms divided by height in meters squared. Such obesity affects about 5% of the American population (1). The incidence in South Africa may be similar.
In contrast to the often short term gains made be dieting and medication, surgery offers a potential long term answer to the seriously obese and those with possible lethal medical complications of obesity. There is no doubt that the blood lipid profile, diabetes mellitus and hypertension show rapid improvement in the first few years post operatively. Base line figures are however often restored in 3 to 4 years. This is at the same time as the metabolic consequences of surgical therapy become manifest.
Thirty years ago the surgical procedures of choice were the gastric bypass operations designed to induce malabsorption. Gastric bypass has always been associated with weight loss as evidenced by the “complications” of gastric surgery for peptic ulcer disease. The principal gastric bypass operation is the Roux-en-Y. This has been shown to be cost effective when compared to no treatment (4). Some of this benefit is related to the dumping these patients experience when eating carbohydrate rich meals. Small frequent meals can however minimize these effects.
The first surgical approach to bariatric surgery was the jejunocolic bypass which was soon replaced by the jejunoileal bypass because of the high incidence of metabolic and infectious complications. The complications were however similar and these procedures were abandoned. Some of the problems were probably due to the blind loop that was introduced by these procedures. More recently biliarypancreatic bypass delivers the digestive enzymes to the distal ileum leaving the food to pass through the small bowel undigested. This remains a major open operation with classical complications of such surgery.
Gastric operations designed to reduce the gastric volume and thereby induce early satiety have become more popular. Initial open gastric banding and segmenting have given way to laparoscopic techniques. Generally these are safe operations with low morbidity. Vertical-band gastroplasty has been used widely. It involves elongation of the esophagus with a fixed termination midway along the lesser curvature of the stomach. Laparoscopic insertion of a gastric ring with a subcutaneous inflatable pouch has been described. Laparoscopic devices have been approved by the FDA for the treatment of morbidly obese with co-morbid conditions.
While laparoscopic techniques are attractive from the peri-operative morbidity point of view patients often adapt their diets to include more liquids to bypass the anatomic obstruction caused by the surgery to solid food. This has helped to sustain the interest in surgically induces malabsorption.
It has been shown that the more invasive surgery produces better weight loss but metabolic complications include iron malabsorption and vitamin B12 deficiency. The rapid weight loss is associated with a high incidence of gallstones.
Other procedures such as jaw wiring have not been shown to have long term benefit. Intragastric balloons appear to offer a simple solution but cause local gastric wall damage and their benefit tends to wane with dietary modification. Liposuction may improve the appearance of particularly fat areas but like rose pruning only lasts for the season.
Because of all the problems associated with open surgery, laparoscopic techniques are now being performed more often. The number of these procedures being undertaken in the USA is increasing exponentially. In South Africa the procedures are not widely available and generally not funded by the medical aids. Patients with life threatening obesity may attract some funding by some “full service” medical insurers. Generally obesity is still viewed as a self induced disease similar to other substance addictions.
Insulin resistance used to be a term associated with the need for increased doses of insulin to reduce a patients blood sugar levels. It was thought to be due to increased antibodies against foreign proteins in the insulin preparation. Classically insulin resistance has formed part of the pathogenesis of type 2 diabetes. Recently it has been associated with obesity and other components of the “metabolic syndrome”.
As a patient becomes obese insulin resistance appears as a common metabolic association. This may lead to type 2 diabetes mellitus and the associated hyperinsulinemia to hypertension and an abnormal lipid profile. These in turn promote atherosclerosis. This quartet of abdominal obesity, hypertension, diabetes, and dyslipidemia – has been called the metabolic syndrome, syndrome X, and the obesity dyslipidemia syndrome [1,2,4-6].
The role of hyperinsulinism and insulin resistance in hypertension, atherosclerosis and type 2 diabetes is still controversial. Adding a fasting insulin measurement to the lipid profile when evaluating patients with obesity may enable early treatment of the metabolic syndrome before the metabolic complications set in. Treatment with metformin which increases insulin sensitivity prevents the onset of clinical diabetes. The usefulness of metformin in treating obesity and preventing type 2 diabetes, hypertension and atherosclerosis remain to be seen. Traditional dieting and exercise programs to reduce weight still offer the most efficient path to prevention of the ”metabolic syndrome” but the addition of metformin appears to offer some advantage.
1 The spread of the obesity epidemic in the United States, 1991-1998. Mokdad AH; Serdula MK; Dietz WH; Bowman BA; Marks JS; Koplan JP JAMA 1999 Oct 27;282(16):1519-22.
Differentiated long-term effects of intentional weight loss on diabetes and hypertension. Sjostrom CD; Peltonen M; Wedel H; Sjostrom L. Hypertension 2000;36:20-5.
Health Outcomes of Severely Obese Type 2 Diabetic Subjects 1 Year After Laparoscopic Adjustable Gastric Banding. Dixon JB; O'Brien PE. Diabetes Care 2002;25:358-363.
Cost-effectiveness of gastric bypass for severe obesity. Craig BM; Tseng DS. Am J Med 2002;113:491-8.