Improving insulin resistance in obese youth: Choose your measures wisely

Authors

  • GABRIEL Q. SHAIBI,

    Corresponding author
    1. Department of Kinesiology, Center for Metabolic Biology, and College of Nursing & Health Innovation, Arizona State University, Phoenix, AZ
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  • JAIMIE N. DAVIS,

    1. Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA
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  • MARC J. WEIGENSBERG,

    1. Department of Pediatrics, Keck School of Medicine, University of Southern California, Los Angeles, CA
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  • MICHAEL I. GORAN

    1. Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA
    2. Department of Physiology and Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, CA
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College of Nursing & Health Innovation 500 N. 3rd St. Phoenix, AZ 85004, USA. Fax: 602 496 0921. E-mail: Gabriel.Shaibi@asu.edu

Abstract

Objective. The purpose of this investigation was to compare the homeostasis model assessment of insulin resistance (HOMA-IR) to more direct measures of insulin action before and after lifestyle interventions in obese Latino youth. Study design. Eleven obese Latino boys (age 15.1 ± 1.6 years, body mass index (BMI) percentile 97.3 ± 3.5%) and twenty obese Latina girls (age 14.7 ± 1.8 years, BMI percentile 96.6 ± 3.6%) participated in two distinct lifestyle interventions. Boys participated in a 16-week exercise intervention and girls participated in a 12-week nutrition education program. Insulin sensitivity was determined by the frequently sampled intravenous glucose tolerance test (FSIVGTT) in boys and by a 3-hour oral glucose tolerance test with multiple sampling calculations for the whole-body insulin sensitivity index (WBISI) in girls. HOMA-IR was measured for both groups. Results. HOMA-IR was correlated at baseline to the FSIVGTT (r = −0.57, p = 0.07) and the WBISI (r = −0.78, p<0.01) and at follow-up (FSIVGTT: r = −0.81, p<0.003; WBISI: r = −0.71, p = 0.001). Post-intervention, insulin sensitivity increased 45% in the boys and 34% in the girls; however, these improvements were not reflected by significant changes in HOMA-IR. Conclusions. Improvements in insulin sensitivity following an intervention measured either by the FSIVGTT or an OGTT were not detected by HOMA-IR. Researchers and clinicians should exercise caution in relying on fasting indices, such as HOMA-IR, to determine the impact of lifestyle interventions on insulin sensitivity in overweight youth.

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