Theresa Hegmann, MPAS, PA-C, DEPARTMENT EDITOR

Treating obesity: New advice from the American College of Physicians

Theresa Hegmann, MPAS, PA-C

The author is Clinical Assistant Professor and Director of Curriculum and Evaluation, Physician Assistant Program, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City. She has indicated no relationships to disclose relating to the content of this article.

We know a lot about obesity. We know that it is a growing problem in the United States, now approaching epidemic proportions.¹ Obesity is associated with many leading causes of death and disability and is thus exceedingly costly to our health care system. Overweight (defined as a body mass index [BMI] of greater than 25 kg/m²) and obesity (BMI of 30 kg/m² or greater) are significantly associated with cardiovascular disease (CVD), diabetes, hypertension, hyperlipidemia, asthma, stroke, sleep apnea, and arthritis, among other conditions.^2-4 We also know that compared to the normal weight category, obesity is associated with excess mortality—though the figures published recently in JAMA suggest that the impact of obesity on mortality may be lessening over time.⁵

What we don’t know

What we don’t know about obesity is how to treat it effectively. We know we should—the Healthy People 2000 and 2010 guidelines have emphasized this, and the United States Preventive Services Task Force (USPSTF) recommends screening all adults for obesity by measuring BMI and providing intensive counseling and behavioral interventions for obese adults.^6,7 Unfortunately, this can be treacherous (and time-consuming) territory. Once you raise the topic of weight loss, what advice should you give?

Increasingly, patients are asking about medications and surgery. Until recently, there has been considerable controversy over these interventions, but now clinicians have a new tool available to them: a clinical practice guideline from the American College of Physicians (ACP).⁸ This guideline is based on two extensive meta-analyses undertaken by the Southern California Evidence-Based Practice Center and is meant to complement the 2003 USPSTF guidelines by providing evidence-based recommendations for the use of pharmacologic and surgical treatments of obesity.

This ambitious project addresses a very significant issue in primary care, but we must remember that the guidelines apply only to patients with a BMI of 30 kg/m² or greater. Furthermore, even though meta-analyses can provide a powerful means of summarizing data across several primary studies and may increase the precision of the overall result, they are limited by several factors—most notably by the quality of the original studies included in the review and by the possibility that studies with negative or unfavorable outcomes may never go to publication.⁹ If the primary studies used in a meta-analysis are methodologically weak or significantly biased, the end result can be a demonstration of the “garbage in—garbage out” phenomenon on a grand scale.

What did the evidence show?

The authors of the meta-analysis on pharmacologic treatment of obesity did an extensive search of both published and unpublished studies using very specific criteria. To be included in their analysis, a study had to be a controlled clinical trial in humans that reported weight loss outcomes over at least a 6-month period and that enrolled patients with a BMI of 27 kg/m² or greater. The pharmaceutical agents reviewed included all the medications currently approved by the FDA for weight loss, as well as several medications that are sometimes used off-label for the purpose. The authors concluded that “sibutramine [Meridia], orlistat [Xenical], phentermine [Adipex P], probably diethylpropion [Tenuate], probably fluoxetine [Prozac], bupropion [Wellbutrin], and topiramate [Topamax] promote weight loss for at least 6 months when given along with recommendations for diet (and possibly other behavioral and exercise interventions).”⁴

However, their findings have some very significant caveats. The amount of extra weight loss that could be attributed to the medications was less than 5 kg (11 lb) at 1 year, and the authors found no evidence to suggest that any of the drugs was more effective than the others. All the drugs have significant side effects, which vary dramatically across the group. The monthly cost of the medications also varied dramatically, from around $39 for phentermine, to $104 for sibutramine, to $160 or more for topiramate and orlistat.

This meta-analysis served most effectively to point out the many limitations in our current state of knowledge regarding the use of medications to promote weight loss. We have virtually no information on long-term health outcomes. Does use of these medications help to prevent diabetes or improve glucose tolerance? What about reducing BP or cholesterol or CVD end points such as stroke or MI? With the exception of a single study of orlistat that did show some evidence of decreased incidence of diabetes, the studies just haven’t been done.

Surgery for obesity

The authors of the meta-analysis on surgical treatment of obesity faced somewhat different obstacles, foremost of which was a lack of randomized, controlled trials for review. This forced them to rely more on observational studies and even to some extent on case-series data. In contrast to the literature on pharmacologic therapy, though, the surgical literature contained more data on mortality, complication rates, and control of obesity-related conditions, so the authors were able to include these important end points in their analysis. Even though most of the evidence reviewed in this meta-analysis was observational in nature, the fact that surgical treatment of obesity was associated with weight loss an order of magnitude greater than that in nonsurgical comparison groups allowed the authors to conclude that surgical treatment is superior to nonsurgical treatment for patients with a BMI of 40 kg/m² or greater.¹⁰ In patients with BMIs between 35 and 39 kg/m², the data strongly supported surgical therapy, but a lack of studies including nonsurgical comparison groups made the available data inconclusive.

The amount of weight loss seen with surgery was in the range of 20 to 30 kg (44–66 lb), maintained for 10 years or longer, and accompanied by significant improvements in obesity-related conditions including diabetes, hyperuricemia, lipid abnormalities, and sleep apnea at the 10-year follow-up point. Evidence was also sufficient to conclude that gastric bypass procedures generally result in more weight loss than gastroplasty procedures. Mortality rates for surgical procedures were less than 1%, though unfortunately, there is no evidence from controlled trials to allow comparison of mortality rates for surgical versus medical therapy of obesity.

The final recommendations

The new ACP clinical practice guideline is based on two thorough meta-analyses of the existing medical literature on treatment of obesity. The overall findings were summarized in the form of four recommendations:

As with any clinical practice guideline, this one comes with limitations: It applies only to patients with a BMI higher than 30 kg/m², is only a guide, and expires in 5 years (or if an update is issued). Even with these stipulations, the ACP guideline provides a potent tool for primary care clinicians trying to deal with the difficult and frustrating task of treating obesity. Now when our patients ask us about medications or surgery, at least we can give them an evidence-based answer.    

REFERENCES

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