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Surgical management of severe obesity

Vivian M Sanchez, MD
Benjamin E Schneider, MD
Edward C Mun, MD, FACS


UpToDate performs a continuous review of over 350 journals and other resources. Updates are added as important new information is published. The literature review for version 14.2 is current through April 2006; this topic was last changed on May 15, 2006. The next version of UpToDate (14.3) will be released in October 2006.

INTRODUCTION — Obesity is a chronic disease that is increasing in prevalence in the United States and worldwide. Defined as a body mass index (BMI) >30 kg/m2, the percentage of obese men nearly doubled between 1991 and 1998, and the percentage of obese women increased by 50 percent. More than 31 percent of adults in the United States (approximately 61 million people) are obese [1,2]. Furthermore, more than 64 percent of Americans are overweight (BMI 25 kg/m2). (See "Overview of therapy for obesity in adults" section on Prevalence)

There are several well-established health hazards associated with obesity including type 2 diabetes, heart disease, stroke, certain cancers, osteoarthritis, liver disease, obstructive sleep apnea, and depression (show table 1). The risk of development of complications rises with increasing adiposity while weight loss can reduce the risk. (See "Health hazards associated with obesity in adults").

There are many behavioral, medical, and surgical options for achieving weight loss. This topic review will focus on surgical procedures, which have been collectively referred to as "bariatric" surgery (from the Greek words "baros" meaning "weight" and "iatrikos" meaning "medicine"). Complications of these procedures are discussed separately. (See "Complications of bariatric surgery"). A general approach to the management of obesity is also presented separately. (See "Overview of therapy for obesity in adults").

DEFINITIONS — Body mass index (BMI) is considered to represent the most practical measure of a person's adiposity. It is calculated by dividing the weight in kilograms by the height in meters squared (kg/m2). In adults. a BMI of:

25 to 29.9 kg/m2 is considered overweight
30 to 34.9 kg/m2 is considered obese (class I obesity)
35 to 39.9 kg/m2 is considered moderately obese (class II obesity)
40 to 49.9 kg/m2 is considered severely (or extremely or morbidly) obese (class III obesity)
>50.0 kg/m2 is considered super morbidly obese (class IV obesity)
EFFECTIVENESS OF BARIATRIC SURGERY — The goal of surgery is to reduce the morbidity and mortality associated with obesity and to improve metabolic and organ function. Several studies have demonstrated that bariatric surgery is effective in achieving these objectives, while having additional benefits such as reducing monthly medication costs and the number of sick days and improving quality of life [3-13].

At least two meta-analyses have summarized data from various studies [14,15]. One included 136 studies in which patients had undergone a variety of bariatric procedures:

The mean overall percentage of excess weight lost was 61 percent (95% CI 58-64%), varying according to the specific bariatric procedure performed
30-day mortality was 0.1 percent for purely restrictive procedures (defined below), 0.5 percent for gastric bypass, and 1.1 percent for biliopancreatic diversion or duodenal switch.
Diabetes completely resolved in 77 percent and resolved or improved in 86 percent.
Hyperlipidemia improved in 70 percent or more of patients.
Hypertension resolved in 62 percent and resolved or improved in 79 percent.
Obstructive sleep apnea resolved in 86 percent and resolved or improved in 84 percent.
A second meta-analysis that included 147 studies concluded that the evidence supporting a benefit of bariatric surgery was strongest in patients with a BMI of >40 while the benefits in those with BMIS of 35 to 39 were less clear [15]. Greater weight loss was observed with gastric bypass procedures compared with gastroplasty. Overall mortality was less than 1 percent while adverse events occurred in approximately 20 percent of patients. A laparoscopic approach resulted in fewer wound complications compared with an open approach.

The striking benefits on important obesity-related morbidity contrast with relatively disappointing results in the management of severe obesity with medical and behavioral therapy. The Swedish Obese Subjects Trial (SOS) is the largest trial comparing surgical versus medical treatment of morbid obesity. A total of 6328 obese (BMI >34 kg/m2 for men and >38 kg/m2 for women) subjects were recruited of whom 2010 underwent surgery for obesity (gastric banding, gastroplasty or gastric bypass) while 2037 chose conventional treatment. Although the study was not randomized, there was an attempt to match patients by relevant covariates. Begun in 1987, the SOS has spawned multiple publications; the following summarizes the major observations [16-24]:

After two years, weight had increased by 0.1 percent in the control group while it had decreased by 23 percent in the surgery group [24]. After ten years, weight had increased by 1.6 percent and decreased by 16 percent, in the two groups respectively. Energy intake was lower and the proportion of physically active subjects higher in the surgery group throughout the observation period. Two and ten-year rates of recovery were better for diabetes (Odds ratio {OR} 8.42 and 3.45, respectively), hypertriglyceridemia (5.28 and 2.57, respectively), low levels of high-density lipoprotein cholesterol (5.28 and 2.35, respectively), hypertension (1.72 and 1.68, respectively) and hyperuricemia (5.36 and 2.37, respectively). There was no difference in rates of recovery from hypercholesterolemia.
The surgery group had lower two and ten-year incidence rates of diabetes (OR 0.14 and 0.25, respectively), hypertriglyceridemia (OR 0.29 and 0.61, respectively) and hyperuricemia (OR 0.22 and 0.49, respectively). There were no significant differences in the incidence of hypercholesterolemia and hypertension.

Surgically treated patients were significantly less likely to require medications for cardiovascular disease or diabetes at two and six years (risk ratio 0.56 to 0.77) [20]. Among those not already requiring such medications, surgery reduced the proportion who required initiation of treatment (risk ratio 0.08 to 0.80).
Costs of medications were reduced significantly in the surgically treated group [21].
Surgically treated patients had dramatic improvement in scores on validated measures of quality of life compared with only minor and sporadic improvement in medically treated patients at two years [16]. The magnitude of benefit was related mostly to the degree of weight loss, which was greater in the surgical group. Similar benefits were observed on validated batteries of psychiatric dysfunction [22].
Although these data would appear to make a compelling argument for treatment of obese diabetic patients with surgery, there have been few well-designed, randomized, prospective trials comparing a specific surgical approaches to optimal medical care. One such study found that laparoscopic adjustable gastric banding was significantly more effective than medical management at two years follow-up in patients with mild to moderate obesity (BMI 30 to 35 kg/m(2)) [25]. Mean excess weight loss was 87 percent in the group randomized to laparoscopic adjustable gastric banding compared with only 22 percent in the optimal medical care group.

Thus, the optimal surgical approach for improvement of diabetes and the cost-effectiveness are unclear. One study suggested that insulin sensitivity improved in proportion to weight loss with the use of predominantly restrictive procedures but was reversed completely by predominantly malabsorptive approaches long before normalization of body weight [26].

The above benefits appear to translate into a reduction in mortality. One of the largest population-based studies to address this issue included 1035 patients who had undergone bariatric surgery who were compared with an age- and gender-matched severely obese control population identified from a population database [3]. Patients who had undergone bariatric surgery were significantly less likely to develop cardiovascular disease, cancer, and endocrine, infectious and psychiatric disorders although they were more likely to develop digestive diseases. The overall mortality rate in the bariatric cohort (0.7 percent) was significantly lower than controls (6.2 percent, RR 0.11, 95% CI 0.04-0.27).

INDICATIONS — Indications for the surgical management of morbid obesity were outlined by the National Institutes of Health (NIH) Consensus Development Panel in 1991 and continue to represent generally-accepted guidelines (show table 2) [27]. Potentially eligible patients should:

Be well-informed and motivated
Have a BMI >40
Have acceptable risk for surgery
Have failed previous non-surgical weight loss
The NIH also suggested that adults with a BMI >35 who have serious comorbidities such as severe diabetes, sleep apnea, or joint disease may also be candidates.