The purpose of this investigation was to expand the evaluation of Normal Weight Obesity (NWO) and its association with insulin resistance using a nationally representative sample of U.S. adults. A cross-sectional study including 5,983 subjects was conducted. Body fat percentage was assessed using dual energy X-ray absorptiometry (DXA). Expanded Normal Weight Obesity (eNWO) categories (pairings of BMI and body fat percentage classifications) were determined by standard cut-points for BMI and the gender specific median for body fat percentage. Homeostatic Model Assessment-Insulin Resistance (HOMA-IR) levels were used to index insulin resistance. Mean ± SE values were as follows: BMI: 27.9 ± 0.2 (women) and 27.8 ± 0.1 (men); body fat percentage: 40.5 ± 0.2 (women) and 27.8 ± 0.2 (men); HOMA-IR: 2.04 ± 0.05 (women) 2.47 ± 0.09 (men). HOMA-IR differed systematically and in a dose-response fashion across all levels of the eNWO categories (F = 291.3, P < 0.0001). As BMI levels increased, HOMA-IR increased significantly and within each BMI category, higher levels of body fat were associated significantly with higher levels of HOMA-IR. Both high BMI and high body fat percentage are strongly related to insulin resistance. In this study, insulin resistance increased incrementally according to BMI levels primarily and body fat levels secondarily. Consequently, due to the costs associated with precisely measuring body fat, and the accuracy of using BMI independently, we recommend that BMI be used in its standard form to predict insulin resistance and not be supplemented with an estimate of body fat.



College and Department

Life Sciences; Exercise Sciences



Date Submitted


Document Type





body fat percentage, HOMA-IR, BMI, metabolic function