The utility of skinfold thickness for estimating insulin resistance and serum triglycerides in adolescents

Abstract

Skinfold thickness has long been found to be highly correlated with total body fat. Yet it remains largely underutilized in comparison to other anthropometric measures. The ability of skinfold thickness to characterize adiposity-related health outcomes should contribute to its utility in studying these outcomes. Objective: To determine comparability of skinfold thickness with whole body total fat, measured by dual energy X-ray absorptiometry (DXA), and their relationships with insulin resistance and serum triglyceride levels in a large sample of US adolescents. The utility of skinfold thickness was evaluated by determining optimum subscapular percentile-cut points for identifying adolescents who are at risk of elevated insulin resistance. Methods: Pooled serial cross-sectional data from the continuous National Health and Nutrition Examination Survey (NHANES) cycles 2001-04 were analyzed. Primary data used included skinfold thicknesses, DXA-based total body fat (DXF), serum insulin and fasting glucose (for homeostasis model assessment of insulin resistance; HOMA-IR), and serum triglycerides. Data from a total of approximately 1500 US youths aged 12-18 years were used in this work. Findings from manuscript one demonstrated that skinfold thickness is comparably associated with both continuous HOMA and the upper quintile of elevated insulin resistance in adolescents as total body fat weight measured with DXA. Similarly, in manuscript two skinfold thickness was comparable to DXA in associations with variation in serum triglycerides, and in predicting adolescents who have elevated serum triglyceride levels. Additionally, subscapular skinfold was found to be better at identifying adolescent girls at risk of elevated serum triglyceride levels than DXA whole-body fat weight. In manuscript three, subscapular skinfold thickness was found to be sufficiently correlated with HOMA-IR to justify identification of age- and sex-specific percentile cut-offs for identifying elevated insulin resistance in adolescents. These new subscapular skinfold percentile cut-offs can be used as a screening tool for identifying US adolescents at risk of elevated insulin resistance, who can then be referred for subsequent follow-up and diagnostic studies. Findings from this dissertation have demonstrated that skinfolds are amply correlated with insulin resistance and serum triglyceride levels, thus supporting their wider use in anthropometric assessment of obesity and its related health outcomes in adolescents.