The U.S. Preventive Services Task Force (USPSTF) grades its recommendations (A, B, C, D, or I) and the quality of the overall evidence for a service (good, fair, poor). The definitions of these grades can be found at the end of the "Major Recommendations" field.
The 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. B recommendation
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. 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 3-5 kg for 1 year or more) 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. 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/m2) adults. The relevant studies were of fair to good quality but showed mixed results. In addition, studies were limited by small sample sizes, high drop-out 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. I recommendation.
The USPSTF found limited data that addressed the efficacy of
counseling-based interventions in overweight adults (as defined by BMI from
25-29.9 kg/m2). 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. BMI, 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 >102 cm (>40 inches) and women with waist circumferences >88 cm (>35 inches) are at increased risk for cardiovascular disease. The waist circumference thresholds are not reliable for patients with a BMI >35.
- Expert committees have issued guidelines defining overweight and obesity based on BMI. Persons with a BMI between 25 and 29.9 are overweight and those with a BMI of >30 are obese. There are 3 classes of obesity: class I (BMI 30-34.9), class II (BMI 35-39.9), and class III (BMI 40 and above). BMI 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
www.nhlbisupport.com/bmi and a table at 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 (see the section, "Effectiveness of Interventions on Weight Loss," below). 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 Food and Drug Administration, can produce modest weight loss (2.6-4.8 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 (longer than 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 to >40 kg) in patients with class III obesity. Clinical guidelines developed by the National Heart, Lung, and Blood Institute (NHLBI) 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.
Definitions:
Strength of Recommendations
The Task Force grades its recommendations according to one
of 5 classifications (A, B, C, D, I) reflecting the strength of evidence and
magnitude of net benefit (benefits minus harms):
A
The USPSTF strongly recommends that clinicians routinely provide [the
service] to eligible patients. The USPSTF found good evidence that [the service]
improves important health outcomes and concludes that benefits substantially
outweigh harms.
B
The USPSTF recommends that clinicians routinely provide [the service] to
eligible patients. The USPSTF found at least fair evidence that [the service]
improves important health outcomes and concludes that benefits outweigh harms.
C
The USPSTF makes no recommendation for or against routine provision of [the
service]. The USPSTF found at least fair evidence that [the service] can improve
health outcomes but concludes that the balance of benefits and harms is too
close to justify a general recommendation.
D
The USPSTF recommends against routinely providing [the service] to
asymptomatic patients. The USPSTF found at least fair evidence that [the
service] is ineffective or that harms outweigh benefits.
I
The USPSTF concludes that the evidence is insufficient to recommend for or
against routinely providing [the service]. Evidence that [the service] is
effective is lacking, of poor quality, or conflicting and the balance of
benefits and harms cannot be determined.
Strength of Evidence
The USPSTF grades the quality of the overall evidence for a service on a 3-point scale (good, fair, poor):
Good
Evidence includes consistent results from well-designed, well-conducted
studies in representative populations that directly assess effects on health
outcomes.
Fair
Evidence is sufficient to determine effects on health outcomes, but the
strength of the evidence is limited by the number, quality, or consistency of
the individual studies, generalizability to routine practice, or indirect nature
of the evidence on health outcomes.
Poor
Evidence is insufficient to assess the effects on health outcomes because of
limited number or power of studies, important flaws in their design or conduct,
gaps in the chain of evidence, or lack of information on important health
outcomes.