Scaling waist girth for differences in body size reveals a new improved index associated with cardiometabolic risk

Our aim was to examine whether a new ratio, waist divided by height^0.5 (WHT.5R), is both independent of stature and a stronger predictor of cardiometabolic risk (CMR) than other anthropometric indices. Subjects (4117 men and 646 women), aged 20-69 years, were assessed for stature (cm), mass (kg), waist, and hip girths (cm) from which body mass index (BMI), waist-to-hip ratio (WHR), waist-to-height ratio (WHTR), and two new indices, a body shape index (ABSI) and WHT.5R, were determined. We used the allometric power law, W = a.HT^b , to obtain a simple body shape index for waist girth (W) to be independent of stature (HT). Physical activity was determined using self-report, and physical fitness was determined using the Bruce protocol. Glucose, total cholesterol, low-density lipoprotein, high-density lipoprotein, triglycerides, and TC/HDL ratio were determined from fasting venous blood samples. A single CMR composite score was derived from log-transformed z-scores of Triglycerides + average blood pressure ((diastolic + systolic)/2) + glucose + HDL (*-1). Results confirmed WHT.5R to be independent of stature and the strongest predictor of CMR, compared with BMI, WC, WHR, ABSI, and WHTR. We also found that CMR scores decline significantly with increasing fitness and physical activity, confirming that being fit and active can compensate for the adverse effects of being fat as measured by all other anthropometric indices. In conclusion, WHT.5R was the best anthropometric index associated with CMR, and being both physically fit and active has a protective effect on CMR, irrespective of weight status.