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Waist Circumference and Cardiometabolic Risk: A Consensus Statement from Shaping America's Health: Association for Weight Management and Obesity Prevention; NAASO, The Obesity Society; the American Society for Nutrition; and the American Diabetes Association

2007; Wiley; Volume: 15; Issue: 5 Linguagem: Inglês

10.1038/oby.2007.632

1930-739X

Samuel Klein, David B. Allison, Steven B. Heymsfield, David E. Kelley, Rudolph L. Leibel, Cathy Nonas, Richard Kahn,

Cardiovascular Disease and Adiposity

Obesity is an important risk factor for cardiometabolic diseases, including diabetes, hypertension, dyslipidemia, and coronary heart disease (CHD).1 Several leading national and international institutions, including the World Health Organization and the National Institutes of Health, have provided guidelines for classifying weight status based on body mass index (BMI) (1)(2). Data from epidemiological studies demonstrate a direct correlation between BMI and the risk of medical complications and mortality rate (e.g., (3)(4). Men and women who have a BMI ≥30 kg/m2 are considered obese and are generally at higher risk for adverse health events than are those who are considered overweight (BMI between 25.0 and 29.9 kg/m2) or lean (BMI between 18.5 and 24.9 kg/m2). Therefore, BMI has become the “gold standard” for identifying patients at increased risk of adiposity-related adverse health outcomes. Body fat distribution is also an important risk factor for obesity-related diseases. Excess abdominal fat (also known as central or upper-body fat) is associated with an increased risk of cardiometabolic disease. However, precise measurement of abdominal fat content requires the use of expensive radiological imaging techniques. Therefore, waist circumference (WC) is often used as a surrogate marker of abdominal fat mass, because WC correlates with abdominal fat mass (subcutaneous and intra-abdominal) (5) and is associated with cardiometabolic disease risk (6). Men and women who have WCs greater than 40 inches (102 cm) and 35 inches (88 cm), respectively, are considered to be at increased risk for cardiometabolic disease (7). These cutpoints were derived from a regression curve that identified the WC values associated with a BMI ≥30 kg/m2 in primarily Caucasian men and women living in north Glasgow (8). An expert panel, organized by the National Heart, Lung and Blood Institute (NHLBI), has recommended that WC be measured as part of the initial assessment and be used to monitor the efficacy of weight loss therapy in overweight and obese patients who have a BMI 40 in (102 cm)] and women [>35 in (88cm)] were derived from WC values that correlated with a BMI ≥30 kg/m2 (2). The National Health and Nutrition Examination Survey III (NHANES III) found that ∼14% of women and ∼1% of men had a “high” WC but a normal BMI (18.5 to 24.9 kg/m2) (35). In addition, ∼70% of women who were overweight (BMI 25.0 to 29.9 kg/m2) had a WC >35 in, and ∼25% of men who were overweight had a WC >40 in. An estimate based on data available from the World Health Organization Monica Project, conducted in >32,000 men and women from Europe, Australia and New Zealand, suggest that ∼10% of participants who had BMI values <30 kg/m2 had a WC above the recommended cutpoints for increased risk (36). It is not known what portion of subjects who had a large WC would have been identified as having increased cardiometabolic risk based on findings from a standard medical evaluation. Therefore, the optimal WC criteria needed to identify patients at increased risk of metabolic disease, who would otherwise not be identified by evaluating BMI and/or other standard cardiometabolic risk factors, is not known, and will likely require adjustments based on BMI, sex, age, and race/ethnicity. . Would assessment of WC in patients who have a BMI ≥25 kg/m2 affect clinical management if NHLBI obesity treatment guidelines are followed? Answer: Probably not. Measurement of WC in clinical practice is not trivial because providing this assessment competes for the limited time available in a busy office practice, and requires specific training to ensure that reliable data are obtained. Therefore, WC should only be measured if it can provide additional information that influences patient management. Based on NHANES III data, 99.9% of men and 98.4% of women would have received the same treatment recommendations proposed by the NHLBI Expert Panel by evaluating BMI and other cardiovascular risk factors, without an assessment of WC (37). However, it is likely that different WC cutpoint values could provide more useful clinical information. For example, an analysis of data obtained from the NHANES III and the Canadian Heart Health Surveys found that BMI-specific WC cutpoints provided a better indicator of cardiometabolic risk than the recommended WC thresholds (35). For normal-weight (BMI 18.5 to 24.9 kg/m2), overweight (BMI 25.0 to 29.9 kg/m2), class I obesity (BMI 30.0 to 34.9 kg/m2) and class II/class III obesity (BMI ≥35.0 kg/m2), the optimal WC cutpoints were 87, 98, 109, and 124 cm in men and 79, 92, 103, and 115 cm in women. Therefore, it is possible that WC measurement could be an effective clinical tool for identifying “metabolically-obese, lean” patients, who might benefit from lifestyle therapy but would not have been considered for treatment because of a normal BMI. WC could also identify “metabolically-normal, obese” subjects, who do not require aggressive obesity therapy because they do not have a marked increase in cardiometabolic risk. WC provides a unique indicator of body fat distribution, which can identify patients who are at increased risk for obesity-related cardiometabolic disease, above and beyond the measurement of BMI. However, the current WC cutpoints recommended to determine health risk (2) were derived by regression from an “obese” BMI and are unlikely to affect clinical management when BMI and other obesity-related cardiometabolic risk factors are already being determined. Therefore, the clinical usefulness of measuring WC, when risk is based on the currently accepted guidelines, is limited. However, WC measurement can sometimes provide additional information to help the clinician determine which patients should be evaluated for the presence of cardiometabolic risk factors, such as dyslipidemia, and hyperglycemia. In addition, measuring WC can be useful in monitoring a patient's response to diet and exercise treatment, because regular aerobic exercise can cause a reduction in both WC and cardiometabolic risk, without a change in BMI (38). Further studies are needed to establish WC cutpoints that can assess cardiometabolic risk not adequately captured by BMI and routine clinical assessments. Selection of the most appropriate WC values will be complex because they are likely influenced by sex, race/ethnicity, age, BMI, and other factors. Nonetheless, it should be possible to determine more useful WC cutpoints than are currently recommended, by carefully reviewing published data and re-evaluating datasets available from existing population studies. These additional analyses will define the future role of WC measurement in clinical practice. S.K. has received research grants from Sanofi-Aventis, Merck, and Takeda for clinical trials; has served as a consultant to Sanofi-Aventis, Amylin Pharmaceuticals, EnteroMedics, Dannon-Yakult, and Merck Pharmaceutical Company. D.A. has received research grants from Frito-Lay and OMP; has served as a consultant to Kraft Foods, Pfizer, Bristol-Myers Squibb, and Bio Era; and has received financial support from Lilly, Pfizer, Merck Pharmaceutical Company, Unilever, Coca-Cola, General Mills, International Life Sciences Institute, GlaxoSmithKline, OMP, Jansen Pharmaceuticals, and Frito-Lay. S.H. is an employee of Merck Pharmaceutical Company. D.K. has received research grants from Novartis Pharmaceuticals, Sanofi-Aventis, and Pfizer; has served as a consultant/advisor to Novartis Pharmaceuticals, Sanofi-Aventis, Pfizer, Merck Pharmaceutical Company, and GlaxoSmithKline; and has been on speaker's bureaus Novartis Pharmaceuticals, Sanofi-Aventis, and Merck Pharmaceutical Company. R.L. has received research grants from GlaxoSmithKline; and has been a consultant/advisor to Amylin Pharmaceuticals, Merck Pharmaceutical Company, Arisaph Pharmaceuticals, and Genaera Corporation. C.N. has been a consultant/advisor to Amylin Pharmaceuticals, GlaxoSmithKline, and Slim Fast.