By Charles Bankhead, Senior Writer, MedPageToday
Reviewed by Zalman S. Agus, MD; Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania
Bariatric surgery leads to significantly greater weight loss and resolution of diabetes and metabolic syndrome as compared with nonsurgical approaches to obesity, a meta-analysis of randomized trials showed.
On average, patients lost an additional 57 lbs when bariatric surgery was added to conventional nonsurgical approaches to weight loss. Patients who had surgery were more than five times as likely to have remission of diabetes and twice as likely to have remission of metabolic syndrome, as compared with patients who were treated only with nonsurgical interventions.
The results add to evidence of bariatric surgery’s efficacy from observational studies, but more long-term follow-up data are needed, Viktoria L. Gloy, PhD, of the University Hospital Basel in Switzerland, and colleagues reported online in BMJ.
“This meta-analysis provides comprehensive evidence that, compared with nonsurgical treatment of obesity, bariatric surgery leads to greater body weight loss and higher remission rates of type 2 diabetes and metabolic syndrome,” the authors concluded.
“The evidence beyond 2 years of follow-up, in particular on adverse events, cardiovascular diseases, and mortality remains unclear and calls for further research on the topic,” they added.
A previous systematic review suggested that bariatric surgery improved weight loss and control of comorbid conditions better than nonsurgical weight-loss interventions did. The review included only three trials, and the number has increased since publication of the review, Gloy and colleagues noted.
To bring the data up to date, they performed a systematic review of the literature, which yielded nine randomized, controlled trials suitable for inclusion. For the analysis, obesity was defined as a body mass index (BMI) ≥30 kg/m2.
The analysis was not limited to a specific type of bariatric procedure, and included studies that used Roux-en-Y gastric bypass, adjustable gastric banding, sleeve gastrectomy, biliopancreatic diversion, or biliopancreatic diversion with duodenal switch. All trials had follow-up of at least 6 months.
The primary objective was to compare the effects of bariatric surgery versus nonsurgical weight-loss strategies on weight loss, cardiovascular risk factors, adverse events, and quality of life.
The meta-analysis comprised 11 studies and a total of 796 patients who had a baseline BMI range of 30 to 52 kg/m2. In all of the trials, patients were randomized to bariatric surgery in addition to nonsurgical intervention versus nonsurgical intervention only.
The trial results showed consistently greater weight loss in patients who had surgery (P<0.001). Differences in the individual trials ranged from 32 to 81 lbs.
Patients randomized to bariatric surgery had an average reduction in waist circumference that exceeded the control group by about 6 inches (P<0.001). The data yielded an unadjusted risk ratio (RR) of 22.1 for remission of diabetes and an adjusted RR of 5.3 in favor of bariatric surgery. Unadjusted and adjusted RRs of 2.4 and 1.5 emerged from an analysis of remission of metabolic syndrome, the latter of which did not achieve statistical significance.
Plasma triglyceride concentrations decreased more (mean difference -0.7 mmol/L) and high density lipoprotein cholesterol concentrations increased more (mean difference 0.21 mmol/L) in the bariatric surgery group, the authors reported. Changes in blood pressure and low density lipoprotein (LDL) concentrations did not differ significantly between groups.
There were no cardiovascular events or deaths reported after bariatric surgery, and the most common adverse event after the procedure was iron deficiency anemia.
Overall, the results did not produce any major surprises, as they confirmed previous evidence from randomized and observational studies, Vivek Prachand, MD, of the University of Chicago, told MedPage Today. The lack of differences in blood pressure and LDL were minor surprises because they are not consistent with findings from previous studies.
Prachand agreed with the authors that longer follow-up is needed to determine the durability of bariatric surgery’s effects, although longer-term data from observational studies suggest the weight loss and metabolic effects are durable.
“The strength of this study is in the pooling together of the evidence of what is now a fairly robust series of level 1, randomized, prospective studies that have been done in the last several years,” Prachand said.
One caveat that nonsurgeons in particular should keep in mind is the fact that the analysis combined results from studies that employed different types of bariatric surgery, he added. The various procedures have advantages and disadvantages, and the choice of procedure should be made after a discussion between the patient and surgeon, leading to an individualized decision based a patient’s clinical characteristics.
The study had some limitations including the relatively small size of the trials. In addition, many of the trials required that participants make serious attempts to lose weight before entering the respective studies. “Thus, the results presented in our meta-analysis may not apply to individuals without prior weight loss attempts,” the authors cautioned.
