Low Cardiorespiratory Fitness Is Associated with Markers of Insulin Resistance in Young, Normal Weight, Hispanic Women.

BACKGROUND

Low cardiorespiratory fitness (CRF) and its decline over time are predictors of the development of diabetes in black and Caucasian women, independent of obesity. It is unclear, however, if the adverse effect of low CRF on the risk of diabetes in Hispanic women is mediated by obesity. Our purpose was to determine the associations of CRF with markers of insulin resistance in 68 normal weight Hispanic women.

METHODS

Obesity indicators included body mass index (BMI), body composition by DXA, and waist circumference. CRF was measured by indirect calorimetry. A glucose tolerance test was used to measure markers of insulin resistance: homeostasis model assessment, fasting insulin, 2-hr insulin, area under the curve insulin, qualitative insulin sensitivity check, and insulin sensitivity index. Pearson correlation and multiple regression analyses were used to identify associations between CRF and markers of insulin resistance. Multivariate ANOVA was used to compare markers of insulin resistance over quartiles of CRF.

RESULTS

Low CRF was significantly associated with all markers of insulin resistance (P < 0.01). These associations were independent of age, BMI, waist circumference, family history of T2DM, and triglycerides (CRF standardized beta range: -0.27 to -0.46, P < 0.05). However, these associations were attenuated when body composition, specifically fat-free mass, was entered into the model (CRF standardized beta range: -0.03 to 0.21, P > 0.05). All markers of insulin resistance improved linearly across CRF quartiles (P < 0.05).

CONCLUSIONS

Our findings suggest that low CRF may be an important predictor of diabetes risk in Hispanic women and that fat-free mass rather than overall body adiposity mediates these relationships.