Screening for Obesity in Adults: Recommendations and Rationale

Summary of Recommendations

The U.S. Preventive Services Task Force (USPSTF) recommends that clinicians screen all adult patients for obesity and offer intensive counseling and behavioral interventions to promote sustained weight loss for obese adults. This is a grade B recommendation. (See Appendix Table 1 for a description of the USPSTF classification of recommendations.)

The USPSTF found good evidence that body mass index (BMI), calculated as weight in kilograms divided by height in meters squared, is reliable and valid for identifying adults at increased risk for mortality and morbidity due to overweight and obesity. (See Appendix Table 2 for a description of the USPSTF classification of levels of evidence.) There is fair to good evidence that high-intensity counseling—about diet, exercise, or both—together with behavioral interventions aimed at skill development, motivation, and support strategies produces modest, sustained weight loss (typically 3 to 5 kg for ≥1 year) in adults who are obese (as defined by BMI ≥30 kg/m ² ). Although the USPSTF did not find direct evidence that behavioral interventions lower mortality or morbidity from obesity, the USPSTF concluded that changes in intermediate outcomes, such as improved glucose metabolism, lipid levels, and blood pressure, from modest weight loss provide indirect evidence of health benefits. No evidence was found that addressed the harms of counseling and behavioral interventions. The USPSTF concluded that the benefits of screening and behavioral interventions outweigh potential harms.

The USPSTF concludes that the evidence is insufficient to recommend for or against the use of moderate- or low-intensity counseling together with behavioral interventions to promote sustained weight loss in obese adults. This is a grade I recommendation.

The USPSTF found limited evidence to determine whether moderate- or low-intensity counseling with behavioral interventions produces sustained weight loss in obese (as defined by BMI ≥30 kg/m ² ) adults. The relevant studies were of fair to good quality but showed mixed results. In addition, studies were limited by small sample sizes, high dropout rates, potential for selection bias, and reporting the average weight change instead of the frequency of response to the intervention. As a result, the USPSTF could not determine the balance of benefits and potential harms of these types of interventions.

The USPSTF concludes that the evidence is insufficient to recommend for or against the use of counseling of any intensity and behavioral interventions to promote sustained weight loss in overweight adults. This is a grade I recommendation.

The USPSTF found limited data that addressed the efficacy of counseling-based interventions in overweight adults (as defined by BMI from 25 to 29.9 kg/m ² ). As a result, the USPSTF could not determine the balance of benefits and potential harms of counseling to promote sustained weight loss in overweight adults.

Clinical Considerations

A number of techniques, such as bioelectrical impedance, dual-energy x-ray absorptiometry, and total body water, can measure body fat, but it is impractical to use them routinely. Body mass index, which is simply weight adjusted for height, is a more practical and widely used method to screen for obesity. Increased BMI is associated with an increase in adverse health effects. Central adiposity increases the risk for cardiovascular and other diseases independent of obesity. Clinicians may use the waist circumference as a measure of central adiposity. Men with waist circumferences greater than 102 cm (>40 inches) and women with waist circumferences greater than 88 cm (>35 inches) are at increased risk for cardiovascular disease. The waist circumference thresholds are not reliable for patients with a BMI greater than 35 kg/m².

Expert committees have issued guidelines defining overweight and obesity based on BMI. Persons with a BMI between 25 and 29.9 kg/m² are overweight, and those with a BMI of 30 kg/m² or more are obese. There are 3 classes of obesity: class I (BMI 30 to 34.9 kg/m²), class II (BMI 35 to 39.9 kg/m²), and class III (BMI ≥ 40 kg/m²). Body mass index is calculated either as weight in pounds divided by height in inches squared multiplied by 703, or as weight in kilograms divided by height in meters squared. The National Institutes of Health (NIH) provides a BMI calculator at http://www.nhlbisupport.com/bmi/ and a table at http://www.nhlbi.nih.gov/guidelines/obesity/bmi_tbl.htm.

The most effective interventions combine nutrition education and diet and exercise counseling with behavioral strategies to help patients acquire the skills and supports needed to change eating patterns and to become physically active. The 5-A framework (Assess, Advise, Agree, Assist, and Arrange) has been used in behavioral counseling interventions such as smoking cessation and may be a useful tool to help clinicians guide interventions for weight loss. Initial interventions paired with maintenance interventions help ensure that weight loss will be sustained over time.

It is advisable to refer obese patients to programs that offer intensive counseling and behavioral interventions for optimal weight loss. The USPSTF defined intensity of counseling by the frequency of the intervention. A high-intensity intervention is more than 1 person-to-person (individual or group) session per month for at least the first 3 months of the intervention. A medium-intensity intervention is a monthly intervention, and anything less frequent is a low-intensity intervention. There are limited data on the best place for these interventions to occur and on the composition of the multidisciplinary team that should deliver high-intensity interventions.

The USPSTF concluded that the evidence on the effectiveness of interventions with obese people may not be generalizable to adults who are overweight but not obese. The evidence for the effectiveness of interventions for weight loss among overweight adults, compared with obese adults, is limited.

Orlistat and sibutramine, approved for weight loss by the U.S. Food and Drug Administration, can produce modest weight loss (2.6 kg to 4.8 kg) that can be sustained for at least 2 years if the medication is continued. The adverse effects of orlistat include fecal urgency, oily spotting, and flatulence; the adverse effects of sibutramine include an increase in blood pressure and heart rate. There are no data on the long-term (>2 years) benefits or adverse effects of these drugs. Experts recommend that pharmacological treatment of obesity be used only as part of a program that also includes lifestyle modification interventions, such as intensive diet and/or exercise counseling and behavioral interventions.

There is fair to good evidence to suggest that surgical interventions such as gastric bypass, vertical banded gastroplasty, and adjustable gastric banding can produce substantial weight loss (28 kg to >40 kg) in patients with class III obesity. Clinical guidelines developed by the National Heart, Lung, and Blood Institute Expert Panel on the identification, evaluation, and treatment of overweight and obesity in adults recommend that these procedures be reserved for patients with class III obesity and for patients with class II obesity who have at least 1 other obesity-related illness. The postoperative mortality rate for these procedures is 0.2%. Other complications include wound infection, re-operation, vitamin deficiency, diarrhea, and hemorrhage. Re-operation may be necessary in up to 25% of patients. Patients should receive a psychological evaluation prior to undergoing these procedures. The long-term health effects of surgery for obesity are not well characterized.

The data supporting the effectiveness of interventions to promote weight loss are derived mostly from women, especially white women. The effectiveness of the interventions is less well established in other populations, including the elderly. The USPSTF believes that, although the data are limited, these interventions may be used with obese men, physiologically mature older adolescents, and diverse populations, taking into account cultural and other individual factors.

The brief review of the evidence that is normally included in USPSTF recommendations is available in the complete recommendation and rationale statement on the USPSTF Web site (http://www.preventiveservices.ahrq.gov).

Recommendations of Others

The Canadian Task Force on Preventive Health Care finds insufficient evidence to recommend for or against BMI measurement in the periodic health examination of the general population and found insufficient evidence to recommend for or against community-based obesity prevention programs (1). The American Academy of Family Physicians (2) and the American College of Obstetricians and Gynecologists recommend periodic measurements of height and weight. The NIH has a 2-step guideline of assessment and treatment management of overweight and obese individuals (3). The American College of Preventive Medicine recommends periodic BMI measurement of all adults and diet and exercise counseling of all adults (irrespective of BMI) and endorses NIH management guidelines (4). The American Diabetes Association has published a position statement that recommends the use of intensive lifestyle modification programs along with standard weight loss strategies for long-term weight loss and maintenance (5).