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.
Acknowledgements
We are grateful to the participants and their families for their involvement in the study as well as the staff at the USC GCRC. This work was supported by the Thrasher Research Fund (02817-1), the Dr. Robert G. Atkins Foundation, the USC Center for Interdisciplinary Research, and the USC GCRC (M01 RR 00043).
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.