Identification of Obesity and Cardiovascular Risk in Ethnically and Racially Diverse Populations: Going Beyond BMI

Obesity, defined as excess fat (adipose) tissue accumulation that may have adverse health effects,¹ is highly prevalent in adults in the United States and worldwide. Accumulated data underscore the cardiometabolic health risks that are associated with obesity in adulthood, including such chronic conditions as Type 2 diabetes as well as cardiovascular disease (CVD).

In this paper, Rao and colleagues call our attention to an important and underemphasized topic: the accurate identification of overweight and obese adults who are at high risk for obesity-related adverse health conditions. Body-mass index (BMI), a surrogate measure of obesity, is commonly used in research as well as in clinical practice to classify individuals as overweight or obese. Current cut points for classifying adults as overweight (BMI ≥25 kg/m2) or obese (BMI >/= 30 kg/m2) are based on a criterion standard supposedly reflecting morbidity and mortality.² Recent evidence, albeit not extensive, suggests that compared to normal weight BMI (20-25 kg/m2), a BMI between the overweight and obese cut points, is associated with lower mortality while a BMI of 30-35 kg/m2 is not associated with increased mortality.³ In addition, research and anecdotal observations have demonstrated that many individuals with a normal BMI have excess levels of adiposity while others have a high BMI and are metabolically “healthy”. ^4,5 The issue of misclassification is particularly relevant for individuals from racial and ethnic minority populations who currently comprise ~ 40% of the US population with predictions indicating they may make up more than half of the population by 2050. ^6,7 Of particular note, current BMI cut points provide a poor estimate of adiposity among Japanese Americans where the optimal BMI for identifying individuals at increased risk for two or more major risk factors for CVD has been estimated at 23.3 kg/m2 for women and 25.3 kg/m2 for men.⁸ Similarly, estimates suggest much lower than current cut points for identifying risk among Asians and Asian Americans ⁹ and lower cutoffs for predicting diabetes among men of Mexican origin as compared with their white non-Hispanic male counterparts.¹⁰

Taken together, as emphasized by Rao and colleagues in this paper, it is time to look beyond BMI in identifying obesity and cardiovascular risk, particularly in ethnically and racially diverse populations. Lessons learned point to the utility of adding another measure of adiposity such as waist circumference (WC) to the clinician’s and researcher’s tool box for capturing adiposity associated with adverse health conditions. The writing group for this paper endorses using WC measured annually in adults and by standard technique.¹¹ Indeed, WC, a measure of abdominal adiposity, correlates with amount of visceral adipose tissue (VAT), which is strongly associated with cardiovascular risk.^12,13 This recommendation is consistent with the AHA/ACC 2013 Guideline for the Management of Overweight and Obesity In Adults.¹⁴ Central to this recommendation is the need to increase knowledge and awareness about the importance of WC as a measure of cardiovascular risk among health care professionals, as well as the public, and the need for training of health care professionals on the accurate measurement of WC.

Going forward, additional research is needed with diverse racial and ethnic populations to determine the usefulness of emerging non-invasive techniques for anthropometric measurements, as well as the utility of incorporating both standard and emerging measures in cardiovascular risk prediction models for these populations. Considering the cardiovascular health of future generations, we have an urgent need to advocate for and conduct additional research focused on the accurate assessment of obesity and cardiovascular risk in children and adolescents of diverse racial and ethnic backgrounds. The future is now!