By Nancy Walsh, Staff Writer, MedPage Today
Published: June 04, 2013
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco
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Bariatric surgery led to greater weight loss and better glycemic control than nonsurgical treatment among patients with diabetes who were mildly obese, but the evidence for long-term efficacy and safety remains limited.
Point out that in long-term follow-up of some studies in the systematic review, weight loss often was not maintained, although improvements in diabetes did remain.
Bariatric surgery led to greater weight loss and better glycemic control than nonsurgical treatment among patients with diabetes who were mildly obese, but the evidence for long-term efficacy and safety remains limited, a systematic review found.
In one of the three randomized studies included in the review, patients who had gastric bypass lost 29.4 kg (64.8 lb) and those who had sleeve gastrectomy lost 25.1 kg (55.3 lbs) over the course of a year, whereas patients on medical therapy lost only 5.4 kg (11.9 lb, P<0 .001="" according="" and="" angeles="" california="" colleagues.="" los="" maggard-gibbons="" md="" melinda="" of="" the="" to="" university="">
In addition, mean hemoglobin (Hb)A1c at 12 months was 6.4% in the gastric bypass group and 6.6% in the sleeve gastrectomy group, compared with 7.5% in the medical therapy group (P<0 .003="" 5="" american="" association.="" in="" journal="" june="" medical="" of="" reported="" researchers="" the="">
"Current evidence suggests that bariatric surgery is associated with more short-term weight loss and better intermediate glucose outcomes than nonsurgical therapy in patients with diabetes and a [body mass index] of 30 to 35," they wrote.
However, "it is unknown whether the benefits observed are durable long term and if these findings might translate into reductions in the microvascular and macrovascular complications of diabetes," they cautioned.
Bariatric surgery has demonstrated success for weight loss and comorbidities in morbidly obese patients whose body mass index (BMI) is 35 kg/m2 and higher, but whether individuals with less severe obesity and diabetes could also benefit has been controversial.
To examine the evidence for this, and to see if outcomes differed with the various procedures, Maggard-Gibbons and colleagues reviewed the literature and identified more than 50 studies with either direct or indirect comparisons.
In two of the three randomized trials, which altogether totaled 290 participants, patients not within the target population of BMI between 30 and 35 kg/m2 (the mean was 37) were included, but the reviewers considered the data to be "informative" nonetheless.
In one of these trials, a similar 13.8% weight loss occurred following gastric banding and intensive medical therapy at 6 months, but weight loss continued for an additional 18 months in the surgery group while the medical group regained most of the weight.
In another randomized trial, patients who underwent gastric banding lost 20 kg (44 lbs) more than patients on medical therapy by 2 years, and fasting glucose in the surgery group was 32.8 mg/dL lower.
"In support of this modest clinical trial evidence are direct comparisons of surgery and nonsurgical therapy in more obese populations and indirect comparisons of the associations between surgical and nonsurgical therapies and the outcomes of weight loss and glycemic control," the reviewers wrote.
For instance, in ten observational cohorts of patients, there were decreases of 3 percentage points in HbA1c 6 to 11 months after gastric bypass, 2.9 points after biliopancreatic diversion, and 2.5 points following sleeve gastrectomy.
And in observational studies of these procedures with follow-up of 1 to 2 years, decreases in HbA1c values ranged from 2.4 to 3.1 percentage points.
There were also several earlier systematic reviews that contributed data. In one review of behavioral weight-loss interventions versus usual care, relatively small changes in weight of 2 to 10 kg (4.4 to 22 lbs) were reported along with decreases in HbA1c of zero to 2 points.
Five other reviews of diabetes medications found decreases of 0.5 to 1 point in HbA1c per drug.
However, in long-term follow-up of some studies in the systematic review, weight loss often was not maintained, although improvements in diabetes did hold up.
There was only one death reported, in a patient who developed a perforation after gastric banding, and other complications following surgery such as infections and hernias were uncommon.
But there have been media reports of other deaths, and information about adverse events specifically in patients with diabetes and milder obesity has been lacking.
Therefore, according to the reviewers, "the evidence is insufficient to reach conclusions about the preferred treatment for diabetes in this target population due to the lack of long-term data on patients who have undergone bariatric surgery."
In contrast, there is abundant long-term data for medical treatment and behavioral interventions, including effects on the vascular outcomes.
Because of these persisting uncertainties, the reviewers concluded that until more data on bariatric surgery for these patients become available, "performance of these procedures in this target population should be under close scientific scrutiny, and additional studies comparing procedures are warranted."
Not everyone agrees with the need for delay, however. Eric Volckmann, MD, of the University of Utah in Salt Lake City, who was not involved in the study, told MedPage Today, "Weight-loss surgery hasn't been studied head-to-head with diabetes, but we do know a lot about the surgery. In the short-term, it does provide superior diabetes control compared with medical management. For many patients, it allows them for the first time in their lives to control their weight and related medical problems including diabetes."
The study was funded by the U.S. Department of Health and Human Services.
The authors also received support from the Agency for Healthcare Research and Quality, the Emergency Care Research Institute, VA Health Services, the Centers for Medicare & Medicaid Services, and the NIH.
Primary source: Journal of the American Medical Association
Maggard-Gibbons M, et al "Bariatric surgery for weight loss and glycemic control in nonmorbidly obese adults with diabetes: a systematic review" JAMA 2013; 309: 2250-2261.