Burden of Disease
Since 1976 to 1980, the prevalence of obesity and overweight in the United States have increased by 134% and 48%, respectively.2 In 2007 to 2008, 40% of men and 28% of women in the United States were overweight and 32% of men and 36% of women were obese. The prevalence of obesity exceeds 30% in most age- and sex-specific groups, with approximately 1 in 20 Americans having a BMI greater than 40 kg/m2.3
Depending on age and race, obesity has been shown to be associated with a 6- to 20-year decrease in life expectancy. The leading causes of death in obese adults include ischemic heart disease, diabetes, certain types of cancer (for example, liver, kidney, breast, endometrial, prostate, and colon), and respiratory diseases.4
To update its 2003 recommendation on screening for obesity and overweight in adults 5, the USPSTF reviewed the current state of the evidence and identified new evidence that addresses previously identified gaps. The USPSTF reviewed new evidence on the benefits and harms of screening and primary carefeasible or referable weight-loss interventions.6 The focus of this update was on nonsurgical interventions.
In 2003, the USPSTF found adequate evidence that BMI is an acceptable measure for identifying adults with excess weight.5 Therefore, the USPSTF did not systematically address clinical screening tests for obesity and overweight in its review.
No new trials were identified that compared screening for obesity in adults with no screening. A total of 58 trials of weight-loss interventions were identified. Of these, 38 trials (13,495 participants) involved behavioral interventions, 18 trials (11,256 participants) involved orlistat plus behavioral interventions, and 3 trials (2652 participants) involved metformin plus behavioral interventions.4 In comparison with studies reviewed for the 2003 recommendation, there were 33 new trials of behavioral interventions, 16 new trials involving orlistat plus behavioral interventions, and 3 new trials involving metformin plus behavioral interventions.4
Behavioral interventions. Behavioral intervention trials were generally of high quality, with 24% rated as good quality. Behavioral trial participants had mean BMIs ranging from 25 to 39 kg/m2, with an average baseline BMI across all trials of 31.9 kg/m2. Fifty-five percent of behavioral trials had participants with clinical or subclinical cardiovascular risk factors, such as impaired glucose tolerance.1
Most of the trials showed that behavioral interventions had a statistically significant effect on weight loss at 12 to 18 months.6 Control group participants lost minimal or no weight, whereas intervention group participants lost 1.5 to 5 kg (3.3 to 11.0 lb), or 4% of baseline weight. Interventions with a greater number of sessions showed more weight loss. Patients who participated in 12 to 26 intervention sessions in the first year generally lost 4 to 7 kg (8.8 to 15.4 lb) (6% of baseline weight) compared with 1.5 to 4 kg (3.3 to 8.8 lb) (2.8% of baseline weight) in those who participated in fewer than 12 sessions.6
An increased number of sessions, or increased treatment intensity, was associated with greater weight loss. Most higher-intensity interventions included self-monitoring, setting weight-loss goals, addressing barriers to change, and strategizing about maintaining long-term changes in lifestyle. However, which of these components was associated with weight loss could not be determined.6 A minimum of 12 sessions was essential to realize BMI reduction and maintenance.
Because direct data from screening trials on long-term health outcomes (for example, death, cardiovascular disease, and hospitalizations) were lacking, the USPSTF examined physiologic risk factors for cardiovascular disease. Two good-quality trials showed that diabetes incidence decreased by 30% to 50% over 2 to 3 years (number needed to treat, 7) with behavioral weight-loss interventions among overweight and obese patients with elevated plasma glucose levels.7, 8 Behavioral weight-loss interventions had a minimal effect on lipid outcomes and showed small reductions in blood pressure and waist circumference.6
Combined pharmacologic and behavioral interventions. Fifty-five percent of behavioral trials and 57% of orlistat trials examined participants with clinical or subclinical cardiovascular risk factors. Metformin trials examined participants with diabetes risk factors.4
Combined behavioral and pharmacologic (orlistat or metformin) interventions resulted in weight loss and improvement in physiologic outcomes. Orlistat led to an average weight loss of about 2.6 kg (5.7 lb), a 1.9-cm decrease in waist circumference, and a decrease in fasting glucose level. Metformin led to a 1.5-cm greater decrease in waist circumference; however, its use for obesity is not approved by the FDA and is thus considered an off-label use. In addition, the USPSTF found no evidence on the maintenance of improvement after discontinuation of medications.6
Behavioral interventions. Possible harms of behavioral weight-loss interventions include decreased bone mineral density and increased fracture risk, serious injuries resulting from increased physical activity, and an increased risk for eating disorders. Although limited data suggest that weight loss may be associated with decreased bone density at the hip, the clinical significance of the bone loss is uncertain. The trials found no evidence that weight-loss interventions are associated with serious injuries or an increased risk for eating disorders, weight cycling, or depression.6
Combined pharmacologic and behavioral interventions. There are concerns about the possible harms of orlistat because of recent FDA reports of severe liver disease and a lack of long-term safety data.9 Orlistat has recently been associated with possible kidney and pancreas damage, but no evidence was found supporting these potential harms.10 Both orlistat and metformin caused mild to moderate gastrointestinal adverse effects that resulted in medication discontinuation.
The USPSTF found adequate evidence that intensive, multicomponent behavioral interventions for obese adults can lead to weight loss, as well as improved glucose tolerance and other physiologic risk factors for cardiovascular disease. Inadequate evidence was found about the effectiveness of these interventions on long-term health outcomes (for example, death, cardiovascular disease, and hospitalizations). Adequate evidence indicates that the harms of screening and behavioral interventions for obesity are small. Therefore, the USPSTF concluded that the net benefit of screening is moderate.
A draft of this recommendation statement was posted for public comment on the USPSTF Web site from 26 October to 23 November 2011. All comments received were reviewed during the creation of the final recommendation statement. Specifically, responses to these comments led to clarification of the definition of intensive and multicomponent in the Clinical Considerations and Discussion sections. The Implementation section was expanded to reflect referral to community-based programs. The Recommendations of Others section was expanded to include recommendations from other professional associations. The Clinical Considerations section was expanded to clarify why overweight was not included in the recommendation statement. The Scope of the Review section was refined to clarify the scope of the update. Some respondents asked about costs. The USPSTF does not consider costs in its appraisal of the effectiveness of a service.
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Final Recommendation Statement: Obesity in Adults …