Aims: We hypothesized that height-corrected abdominal size (supine sagittal abdominal diameter/height ratio [SADHtR] or waist circumference/height ratio [WHtR]) would associate more strongly than body mass index (BMI, weight/height2) with levels of fasting insulin, triglycerides, and three derived biomarkers of insulin resistance.
Methods: Anthropometry, including SAD by caliper, was collected on 4398 adults in the 2011-2014 National Health and Nutrition Examination Survey. For comparison purposes, each adiposity indicator was scaled to its population-based, sex-specific, interquartile range (IQR). For each biomarker we created four outcome groups based on equal-sized populations with ascending values. Multivariable polytomous logistic regression modeled the relationships between the adiposity indicators and each biomarker.
Results: Highest-group insulin was associated with a one-IQR increment of BMI (RR 4.3 [95% CI 3.9-4.9]), but more strongly with a one-IQR increment of SADHtR (RR 5.7 [5.0-6.6]). For highest-group HOMA-IR the RR for BMI (4.2 [3.7-4.6]) was less than that of SADHtR (6.0 [5.1-7.0]). Similarly, RRs for BMI were smaller than those for SADHtR applying to highest-group triglycerides (RR 1.6 vs 2.1), triglycerides/HDL-cholesterol (RR 1.9 vs 2.4) and TyG index (RR 1.7 vs 2.2) (all p < .001). The RRs for WHtR were consistently between those for SADHtR and BMI. The top 25% of insulin resistance among US adults was estimated to lie above adiposity thresholds of 0.140 for SADHtR, 0.606 for WHtR, or 29.6 kg/m2 for BMI.
Conclusions: Relative abdominal size rather than relative weight may better define adiposity associated with homeostatic insulin resistance. These population-based, cross-sectional findings could improve anthropometric prediction of cardiometabolic risk.
Keywords: Anthropometry; Body mass index; Insulin resistance; Obesity, abdominal; Sagittal abdominal diameter; Waist-height ratio.
Published by Elsevier B.V.