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Metabolic syndrome and the role of bariatric surgery
Columnists suggest that bariatric surgery at least be discussed with and considered for morbidly obese patients.
Obesity is a worldwide epidemic. In the United States, it is estimated that 30% of the population is obese (BMI >30) and 5% is morbidly obese (BMI >40). Associated with increased weight is the entity known as metabolic syndrome.
Defined by the Adult Treatment Panel III, metabolic syndrome includes insulin resistance or type 2 diabetes, hypertension, atherogenic dyslipidemia (elevated triglycerides, low HDL) and abdominal obesity. Coronary heart disease, nonalcoholic fatty liver disease, obstructive sleep apnea, PCOS and gastroesophageal reflux are all diseases linked to metabolic syndrome. Thus, the overall health risks associated with this syndrome are substantial and correspond to an increase in mortality.
Non-surgical weight loss is usually ineffective, resulting in modest weight loss rarely sustained beyond six months. Even intensive physician-supervised programs of strict caloric reduction and behavioral modification are rarely effective. Therefore, it has become apparent that a more aggressive approach is warranted, resulting in the exponential growth of bariatric surgery in the last 10 years.
The current U.S. guidelines for bariatric surgery recommend surgery be considered for patients with BMI > 40 or BMI > 35 in the presence of an obesity comorbidity.
In the United States, the most common bariatric procedure is the Roux-en-Y gastric bypass, in which a small gastric pouch is created (typically 15 to 30 cc volume). This small gastric pouch is anastomosed or connected to a segment of small bowel known as the Roux limb which is usually 75 to 150 cm in length. Food passes from the gastric pouch through the Roux limb into the remainder of the small bowel. The gastric bypass has traditionally been thought to achieve weight loss through both restrictive (small gastric pouch) and malabsorptive (bypassing 75 to 150 cm of small bowel absorption) mechanisms. However, hormonal mechanisms such as via ghrelin, glucagon-like peptide-1 and peptide YY are increasingly thought to play a substantial role in post-gastric bypass weight loss.
 Ani J. Fleisig |  Brant K. Oelschlager |
A recent meta-analysis including 22,094 patients evaluated the impact of bariatric surgery on excess weight loss (EWL) and reduction of co-morbidities. For those patients that underwent gastric bypass (7,047), the meta-analysis showed that EWL was 65.7% with 83.7% resolution of diabetes, 67.5% resolution of hypertension and 96.9% improvement in hyperlipidemia. Therefore, with the substantial loss in weight, there was reversal of or marked improvement in metabolic syndrome. Most studies in the meta-analysis, however, were uncontrolled case studies with less than two years of follow-up.
The Swedish Obese Subjects study was a large prospective, nonrandomized, 10-year study comparing 2,010 patients who underwent bariatric surgery with 2,037 patients who underwent non-surgical weight loss management. Although the follow-up rate was 74.5% at 10 years, the study demonstrated persistent benefit in the bariatric surgery population in terms of sustained EWL and resolution of metabolic syndrome.
In 2001, the FDA approved the laparoscopic adjustable gastric band (LAGB), which wraps a silicone balloon around the proximal portion of the stomach. This apparatus is attached to flexible tubing that is connected to a subcutaneous access port. When saline is injected into this port, the balloon expands, narrowing the gastric lumen, thereby limiting the capacity of the stomach to accommodate food. In the United States, a series of 1,014 consecutive cases demonstrated EWL of 64.3% at two years. Although effects on metabolic syndrome were not reported in this study, data from international groups show improvement, albeit less profound than after gastric bypass.
A prospective, randomized, controlled study from Melbourne, Australia assigned 80 mildly-to-moderately obese (BMI 30 to 35) patients to either LAGB or non-surgical weight loss therapy. At one year, EWL was 87.2% vs. 21.8%, respectively. In addition, there was reversal of metabolic syndrome in 92.8% of the LAGB patients compared with 36% of the non-surgical weight loss study group. Although this was a small trial with a short follow-up period, it is the only recent truly randomized, controlled bariatric study. This study not only provides strong direct evidence for reduction in the metabolic syndrome after bariatric surgery but also raises the question of whether there should be broader BMI criteria.
Bariatric surgery is an effective weight loss tool with positive, durable results and unparalleled effects on reducing the metabolic syndrome and obesity-related death. Therefore, bariatric surgery should at least be discussed with and considered for morbidly obese patients. Perhaps, BMI criteria for bariatric surgery in the United States should be lowered in the future if more evidence confirms the positive outcomes in patients with BMI less than 35.
Ani J. Fleisig, MD, is an Acting Instructor and Senior Fellow in the Center for Videoendoscopic Surgery in the Department of General Surgery at the University of Washington.
Brant K. Oelschlager, MD, is an Associate Professor and Director of the Center for Videoendoscopic Surgery, Director of the Swallowing Center and Director of Bariatric Surgery in the Department of Surgery at the University of Washington.
For more information:
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