Effect of bariatric surgery on the metabolic syndrome: a population-based, long-term controlled study

Abstract

Objective: To assess the effect of weight loss by bariatric surgery on the prevalence of the metabolic syndrome (MetS) and to examine predictors of MetS resolution.

Patients and methods: We performed a population-based, retrospective study of patients evaluated for bariatric surgery between January 1, 1990, and December 31, 2003, who had MetS as defined by the American Heart Association/National Heart, Lung, and Blood Institute (increased triglycerides, low high-density lipoprotein, increased blood pressure, increased fasting glucose, and a measure of obesity). Of these patients, 180 underwent Roux-en-Y gastric bypass, and 157 were assessed in a weight-reduction program but did not undergo surgery. We determined the change in MetS prevalence and used logistic regression models to determine predictors of MetS resolution. Mean follow-up was 3.4 years.

Results: In the surgical group, all MetS components improved, and medication use decreased. Nonsurgical patients showed improvements in high-density lipoprotein cholesterol levels. After bariatric surgery, the number of patients with MetS decreased from 156 (87%) of 180 patients to 53 (29%); of the 157 nonsurgical patients, MetS prevalence decreased from 133 patients (85%) to 117 (75%). A relative risk reduction of 0.59 (95% confidence interval [CI], 0.48-0.67; P<.001) was observed in patients who underwent bariatric surgery and had MetS at follow-up. The number needed to treat with surgery to resolve 1 case of MetS was 2.1. Results were similar after excluding patients with diabetes or cardiovascular disease or after using diagnostic criteria other than body mass index for MetS. Significant predictors of MetS resolution included a 5% loss in excess weight (odds ratio, 1.26; 95% CI, 1.19-1.34; P<.001) and diabetes mellitus (odds ratio, 0.32; 95% CI, 0.15-0.68; P=.003).

Conclusion: Roux-en-Y gastric bypass induces considerable and persistent improvement in MetS prevalence. Our results suggest that reversibility of MetS depends more on the amount of excess weight lost than on other parameters.

Figure 1. Change in Metabolic Syndrome Components

^aBaseline and follow-up prevalence of Metabolic Syndrome components in bariatric surgery and non-operative patient groups.

Figure 2. Change in Metabolic Syndrome Parameters

^aChange in each of the five components of the Metabolic Syndrome and in the prevalence of the Metabolic Syndrome as defined by the American Heart Association / National Heart, Lung and Blood Institute. Significant changes (P<0.05) are represented by an asterix (*). ^bAbbreviations: TG – Triglycerides; HDL – High Density Lipoprotein Cholesterol; HTN – Hypertension; MetS – Metabolic Syndrome