Are Body Mass Index and Waist Circumference the Best Predictors of Cardiometabolic Risk?

by Bianca Garilli, ND

Body mass index (BMI) is frequently utilized in clinical practice to assess for risk of cardiometabolic disease (CMD). High BMI measurements are associated with insulin resistance along with other markers of CMD such as elevated blood glucose and triglycerides, low HDL cholesterol, and elevated blood pressure.¹ By way of review, a BMI > 30 indicates obesity, which is linked to increased risk of chronic illness, particularly CMD; a BMI 25-29 is considered overweight, and a BMI 18.5-24.9 is considered normal or “lean”.² BMI, however, does not accurately reflect location of fat deposition, which is important in the case of central adiposity, which is an independent risk factor for CMD but can be difficult and expensive to measure directly and with accuracy.²

A surrogate marker for estimating central adiposity (both subcutaneous and intraabdominal) is waist circumference (WC).¹ A WC ≥40 inches in men or ≥35 inches in women increases the risk of CMD.² Although WC is the currently recommended clinical marker of central fat for CMD risk screening, WC can be cumbersome to measure, may create personal boundary issues for some patients and/or healthcare providers, and although anthropometry methodology exists, the WC measurement techniques can vary between practitioners. WC also does not consider the height nor body structure of the individual. The search, therefore, for a more accurate and convenient measurement of central adiposity has yielded more recently proposed methods:¹

• Height-normalized markers (Body Roundness Index – BRI; Weight-to-Height Ratio – WtoH)
• BMI-normalized markers of central fat distribution without inclusion of plasma lipid parameters (A Body Shape Index – ABSI)
• BMI-normalized markers of central fat distribution with inclusion of plasma lipid parameters (BMI-normalized Visceral Adiposity Index – VAI)

To better determine if these proposed markers would provide accurate estimates of central adiposity (and by extension, risk of CMD), a study investigating WtoH, BRI, ABSI and VAI and their association with insulin resistance and metabolic syndrome was performed in 1965 European individuals aged 49 ± 13 years, with a baseline BMI of 26.7 ± 5.2 from the North-East Italy MoMa Population Study.¹

The study collected data and plasma samples from each participant after a 10-hour overnight fast. In addition to a detailed medical exam and medical history intake, blood pressures on both arms and WC were measured for each participant.¹ At the 5-year mark, 350 randomly selected individuals from the original overweight-obese cohort were invited to participate in the follow-up study;263 individuals accepted. The goal of this follow-up was to assess the predictive values of the central adiposity surrogate measures for insulin resistance (as measured by homeostasis model of insulin resistance [HOMA-IR]) and metabolic syndrome at the 5-year follow up.¹

Results from this study:¹

• WtoH and BRI, although helpful in identifying and predicting future CMD incidence, were similar (not significantly better than) the use of WC or BMI alone
• The BMI-normalized marker without inclusion of plasma lipid parameters (ABSI) did not improve prediction of future CMD complications and in some cases proved to be less accurate than WC or BMI
• BMI-normalization with inclusion of plasma lipid parameters (VAI) did provide accurate identification and enhanced ability (over WC or BMI) to predict metabolic syndrome markers at follow-up 

Why is this Clinically Relevant?

• WC or BMI continue to be the most accurate surrogate measures of central adiposity and CMD risk¹
• Surrogate measures of central adiposity that are height-normalized (WtoH or BRI) or BMI-normalized without lipid biomarker info (ABSI) do not provide additional predictive value over WC or BMI in estimating future CMD risk¹
• Combining BMI info with plasma lipid measurements (VAI) is associated with improved identification of CMD risk when compared to BMI or WC alone¹
• WC, BMI, and VAI are all feasible measurements for a clinical setting, and are significantly cheaper than CT or DXA measurements of adiposity

View the abstract 

Citations

1. Barazzoni R, Cappellari GG, Semolic A, et al. Central adiposity markers, plasma lipid profile and cardiometabolic risk prediction in overweight-obese individuals. Clin Nutr. 2018;S0261-5614(18):30165-1.
2. Klein S, Allison DB, Heymsfield SB, et al. 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. Am J Clin Nutr. 2007;85:1197–1202.