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Waist circumference vs BMI

Waist circumference vs BMI – Obesity

Body mass index (BMI) has long been a predictor of the morbidity and mortality that are due to numerous chronic diseases, including type 2 diabetes, cardiovascular disease (CVD), and stroke. In addition, it has been established that abdominal obesity, assessed by waist circumference (WC), predicts obesity-related health risk, and the weighted evidence indicates that WC coupled with BMI predicts health risk better than does BMI alone. In fact, recent findings indicate that WC is a stronger marker of health risk than is BMI. The purpose of the present study was to determine whether BMI adds to the predictive power of WC in assessing obesity-related health risk. This question was addressed by using metabolic and anthropometric data from the third National Health and Nutrition Examination Survey (NHANES III), which is a large cohort representative of the US population.

Subjects included 14,924 men and women (aged greater than or equal to 17 yrs) in whom measures of WC, height, weight, and metabolic variables were obtained. They were divided into 2 WC groups and 3 BMI groups according to the NIH cutoffs. Within both the normal and high WC categories, normal-weight subjects were older (men only) and had smaller BMIs and WCs than did overweight subjects. The overweight subjects in turn were younger and had smaller BMI and WC values than did the obese subjects within the same WC category. Therefore, even within the same WC category, BMI and WC values were higher in the overweight and obese persons than in those with a normal BMI.

Overweight and obese subjects were–with few exceptions–more likely to have hypertension, dyslipidemia. and the metabolic syndrome than were normal-weight subjects. After adjustment for all of the confounding variables, the odds for all of the comorbidities were higher for the overweight and obese men and women than for the normal-weight subjects (except for high LDL cholesterol in men). After WC was included in the regression model, the odds for many of the comorbidities remained significantly higher in the overweight and obese groups.

The results of the study provide compelling evidence that BMI coupled with WC does not predict an increase in obesity-related health risk better than does WC alone, when the 2 values are examined on a continuous scale. Thus, overweight and obese persons have a health risk that is comparable to that of normal weight persons with the same WC value. The researchers of this study conclude that WC, not BMI, explains obesity-related health risk. Thus, for a given WC value, overweight and obese persons and normal-weight persons have comparable health risks. However, when WC is dichotomized as normal or high, BMI remains a significant predictor of health risk.

I. Janssen, P. Katzmarzyk, R. Ross. Waist circumference and not body mass index explains obesity-related health risk. Am J Clin Nutr 79:379-384 (February 2004) [Correspondence: R. Ross, School of Physical and Health Education, Queen’s University, Kingston, ON K7L 3N6, Canada. E-mail: rossr@post.queensu.ca]

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