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Comparative Effectiveness of Bariatric Surgery and Nonsurgical Therapy in Adults With Metabolic Conditions and a Body Mass Index of 30.0 to 34.9 kg/m²

Clinician Summary – Sept. 13, 2013

Comparative Effectiveness of Bariatric Surgery and Nonsurgical Therapy in Adults With Metabolic Conditions and a Body Mass Index of 30.0 to 34.9 kg/m²

Formats

Table of Contents

Research Focus for Clinicians

In response to a request from the public, the Agency for Healthcare Research and Quality (AHRQ) provided support to the Southern California Evidence-based Practice Center to perform a systematic review of the comparative effectiveness and safety of bariatric surgery as a way to treat diabetes and other metabolic conditions in patients with a body mass index (BMI) of at least 30 kg/m2 but less than 35 kg/m2. This review included studies in which participants had a BMI of 30.0 to 34.9 kg/m2 or in which a major subgroup of the study participants were in this BMI range. The systematic review included 54 studies published through September 2012. An online version of this summary provides links directly to the sections of the full report with references for individual findings, inclusion criteria for the studies, and an explanation of the methods for rating the studies and determining the strength of evidence for individual findings. The online version of this summary and the full report can be accessed on the right side of this Web page. This summary is provided to assist in decisionmaking along with a patient’s values and preferences. Reviews of evidence should not be construed to represent clinical recommendations or guidelines.

Background

Bariatric surgery is an accepted practice for patients with a BMI of 40 kg/m2 or greater and for patients with a BMI between 35 and 40 kg/m2 who have significant obesity-related comorbidities such as diabetes, hypertension, cardiovascular disease, dyslipidemia, obstructive sleep apnea, and degenerative arthritis. Currently, the most common types of bariatric surgery include laparoscopic adjustable gastric banding (LAGB), Roux-en-Y gastric bypass (RYGB), biliopancreatic diversion with duodenal switch (BPD/DS), and sleeve gastrectomy. Studies show that these bariatric surgical procedures cause significant weight loss and are more effective at improving diabetes in the short term (up to 2 years) than conventional nonsurgical interventions (diet, exercise, and other behavioral interventions). Diabetes improvement has been shown to start rapidly after surgery, before significant weight loss has occurred. The mechanism for postoperative metabolic improvements has not been fully elucidated and may be, in part, independent of weight loss. This suggests that bariatric surgery may improve metabolic comorbidities even in patients who are not morbidly obese. Thus, bariatric surgery has been suggested as an option for treating diabetes and other metabolic conditions such as impaired glucose tolerance (IGT) in patients with a lower BMI (at least 30 but less than 35 kg/m2).

Conclusion

According to the surrogate measures of blood glucose outcomes, bariatric surgery is an effective treatment for diabetes and IGT in patients with a BMI of at least 30 but less than 35 kg/m2 followed up to 2 years. Weight-loss and glucose-control outcomes achieve greater improvement than typically seen with behavioral interventions (e.g., diet, exercise). Head-to-head comparisons are needed to determine comparative effectiveness among surgical interventions. The rates of short-term adverse effects (cardiovascular, respiratory, gastrointestinal, and metabolic) were low. Reported complications of LAGB include band slippage, leakage, and pouch dilation, and those reported for RYGB include stricture, ulcers, and rarely hemorrhage. While not discussed in the review, it has been suggested that weight regain and recurrence of diabetes might be observed after bariatric surgery. Despite promising short-term outcomes, very few studies of this target population have followup durations greater than 2 years, and the long-term effects of bariatric surgical procedures on major clinical endpoints (all-cause mortality, cardiovascular mortality and morbidity, and peripheral arterial disease) in patients with metabolic conditions and a BMI of 30.0 to 34.9 kg/m2 are not known. Studies comparing surgical intervention to comprehensive care and behavioral interventions to each other are also needed to determine the relative effectiveness of these strategies in the long term.

Clinical Bottom Line

Evidence of Benefits in Adults With Metabolic Conditions and a BMI of 30.0 to 34.9 kg/m2

Evidence of Adverse Effects in Adults With Metabolic Conditions and a BMI of 30.0 to 34.9 kg/m2
Strength of Evidence Scale

High: evidence high
High confidence that the evidence reflects the true effect. Further research is very unlikely to change our confidence in the estimate of effect.

Moderate: evidence medium
Moderate confidence that the evidence reflects the true effect. Further research may change our confidence in the estimate of effect and may change the estimate.

Low: evidence low
Low confidence that the evidence reflects the true effect. Further research is likely to change our confidence in the estimate of effect and is likely to change the estimate.

Insufficient: evidence insufficient
Evidence is either unavailable or does not permit a conclusion.

Outcomes of Surgical and Nonsurgical Treatments in Adults With Metabolic Conditions and a BMI of 30.0 to 34.9 kg/m2
Outcomes (at 1 year unless otherwise specified) Bariatric Surgery* Behavioral Changes** Medications**
* Data are primarily from observational studies and a few RCTs.
** Data are almost entirely from systematic reviews and RCTs.
Oral medications include second-generation sulfonylureas, biguanides, thiazolidinediones, meglitinides, and alpha-glucosidase inhibitors.
Abbreviations: GLP-1R = glucagon-like peptide 1 receptor; LDL = low-density lipoprotein; OR = odds ratio; RCT = randomized controlled trial
Weight A BMI decrease of 5 to 7 kg/m2 (about 15 to 20 kg for someone whose height is 5 ft 6 in). Weight loss of 2.8 kg with diet, exercise, and behavioral interventions versus usual care.
  • Weight gain from 1 to 5 kg with some drugs.
  • Weight loss of 2.8 kg with GLP-1R agonists.
  • No weight change with metformin.
HbA1c, percentage of total hemoglobin Decrease of 2.6 to 3.7 percentage points. Decrease of 0.3 to 2.2 percentage points. Decrease of 0.5 to 1.0 percentage points.
Other metabolic outcomes
  • Significant improvements in diastolic blood pressure, lipids, and metabolic syndrome at 2 years were reported in one RCT. The prevalence of metabolic syndrome decreased by 34.8 percent in that study.
  • Significant decreases in hypertension and cholesterol medications at 1 year were reported in another RCT.
  • Fasting blood glucose was reported to have improved significantly in two RCTs.
  • Improvements in blood pressure and lipids at 1 or 2 years were also reported in observational studies. However, outcomes reporting was inconsistent in these studies.
  • Diet improved fasting glucose (a reduction of 1.3–36.6%) and triglycerides (a reduction of 11.3–58.9%).
  • The PREDIMED study conducted in Spain found that a Mediterranean diet reduced metabolic syndrome prevalence by 13.7 percent at 1 year.
  • The Finnish Diabetes Prevention Study found that behavioral change reduced metabolic syndrome prevalence at 3.9 years (OR = 0.62).
  • Most medications had minimal effects on systolic and diastolic blood pressures with changes less than 5 mmHg.
  • Metformin and second-generation sulfonylureas generally decreased LDL-cholesterol levels.
Prevention of diabetes Data unavailable The U.S. Diabetes Prevention Program (DPP) found diabetes incidence at 10 years reduced by 34 percent by behavioral change versus placebo. The DPP found diabetes incidence at 10 years reduced by 18 percent in the metformin group versus placebo.
Note: There are additional considerations that clinicians should recognize that were not the subject of the review summarized here. Depending on the type of surgery, these might include regular postsurgical monitoring for:
  • Weight regain
  • Recurrence of diabetes
  • Nutritional deficiencies
  • Other postsurgical complications
 

Other Findings of This Systematic Review

Gaps in Knowledge

Resource for Patients

Weight-Loss Surgery for Adults With Diabetes or Prediabetes Who Are at the Lower Levels of Obesity, A Review of the Research for Adults With a BMI Between 30 and 35 is a free companion to this clinician research summary. It covers:

  • A description of BMI and obesity
  • A discussion of diabetes and prediabetes
  • A description of the different types of bariatric surgery
  • A discussion of the amount of weight loss and improvement in blood glucose-control measurements that have been found in studies of bariatric surgery and how these results compare with nonsurgical treatments such as diets and medications
  • A discussion of the side effects and possible harms from the different types of bariatric surgery

What To Discuss With Your Patients and/or Their Caregivers

  • The possible benefits of bariatric surgery for patients with a BMI between 30.0 and 34.9 kg/m2 and with diabetes or IGT
  • The possibility that the patient could be referred to a surgeon who would discuss the different types of bariatric surgery approaches recommended for the patient
  • Whether or not the specific bariatric surgery recommended for the patient would be covered by the patient’s insurance and how that would impact the patient’s decisionmaking
  • The possible adverse effects of bariatric surgery
  • Lifestyle changes and potentially long-term medications that are necessary to fully benefit from bariatric surgery
  • Nonsurgical treatment options for diabetes and other metabolic conditions
  • The expected course of the patient’s diabetes with continued non-surgical therapy

Source

The information in this summary is based on Bariatric Surgery and Nonsurgical Therapy in Adults With Metabolic Conditions and a Body Mass Index of 30.0 to 34.9 kg/m2, Comparative Effectiveness Review No. 82, prepared by the Southern California Evidence-based Practice Center under Contract No. HHSA 290-2007-10062-I for the Agency for Healthcare Research and Quality, June 2013. Available at www.effectivehealthcare.ahrq.gov/weight-loss-surgery.cfm. This summary was prepared by the John M. Eisenberg Center for Clinical Decisions and Communications Science at Baylor College of Medicine, Houston, TX. It was written by Geetha Achanta, Ph.D., Juliet Holder-Haynes, M.D., and Michael Fordis, M.D.

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