Anthropometric predictors of visceral adiposity in normal‐weight and obese adolescents

The prevalence of pediatric obesity, defined as body mass index (BMI) ≥ 95th percentile for age and sex (1), has greatly increased and currently affects 16.0% of US children (2). Pediatric obesity increases the risk of diseases such as the metabolic syndrome (3) and type 2 diabetes (4). The challenge for treating physicians is identifying those at higher risk of obesity-related complications to appropriately target interventions. One complicating factor is that adipose tissue domains carry varying risk levels. Visceral (intra-abdominal) fat deposition is an important risk factor for cardiometabolic complications (5) and all-cause mortality in adult men (6) and for insulin resistance in children (7). Visceral fat measurement entails imaging, via dual-energy X-ray absorptiometry (not validated in children), computerized tomography, or magnetic resonance imaging (MRI) (8); however, this is clinically impractical and expensive. Accurate surrogate anthropometric measurements of visceral vs. subcutaneous adipose tissue (VAT vs. SAT), which can easily be performed in physicians’ offices without extensive training or time, are needed to identify those at highest risk of visceral adiposity and its potential sequelae. Various anthropometric measurements have been proposed as screens for visceral adiposity in both adults (9) and children (10, 11), including BMI, waist circumference (WC), waist–hip ratio (WHR), and more specialized measurements requiring equipment and training (e.g., skinfold thicknesses) (12). Less widely used is the sagittal abdominal diameter (SAD), which measures abdominal thickness at waist level in the supine position. In adults, SAD is associated with dyslipidemia, insulin resistance, hypertension (13), and cardiovascular disease risk (14), and it may be a better predictor of the metabolic syndrome (15) and hyperglycemia (16) than other anthropometric measures such as WC. In adults, SAD correlates highly with VAT mass (17); it has been proposed to be a better measure of VAT than WC or WHR (18), deriving from the theory that gravity moves the subcutaneous fat to the sides while visceral fat projects the abdomen vertically (18–20). However, pediatric data regarding predictive capacity of SAD for visceral adiposity are limited. Adult findings may not be generalizable to children: growth and body composition changes are expected in children, and BMI changes in early adolescence may relate more to lean mass than fat mass acquisition (21). To our knowledge, SAD has only been directly correlated with MRI-measured visceral fat in adolescents in one small study, which included both preadolescents and adolescents and did not adjust for pubertal stage, race, or sex (22). Assessing the utility of SAD in children while specifically accounting for these factors is crucial, given normal puberty-and sex-related changes in body composition (23) and known differences in VAT between populations (24). We hypothesized that, in both normal-weight and obese adolescents, SAD would better correlate with MRI-measured VAT volume than other surrogate anthropometric measurements of adiposity, independent of age, sex, race, and Tanner stage.