Original article
Fitness is a Stronger Predictor of Fasting Insulin Levels than Fatness in Overweight Male Middle-School Children

https://doi.org/10.1016/j.jpeds.2006.12.051Get rights and content

Objective

We studied the relationship between % body fat (%BF), cardiovascular fitness (CVF), and insulin resistance (IR) in overweight middle-school children.

Study design

Middle school children (n = 106, body mass index [BMI] > 95th percentile for age) underwent evaluation of body composition, maximal volume of oxygen utilization (Vo2) uptake/kg lean body mass (Vo2max/kgLBM), and fasting glucose and insulin (FI) concentrations and derived homeostasis model assessment index (HOMAIR).

Results

Both %BF (r = .33, P < .001) and Vo2max/kgLBM (r = −0.42, P < .0001) were significantly correlated with FI. Bivariate regression analysis revealed %BF (P = .008 vs FI, P = .035 vs HOMAIR) and VO2max/kgLBM (P < .001 vs FI, P = .009 vs HOMAIR) to be independent predictors of insulin sensitivity. In males, VO2max/kgLBM was a better predictor of FI and HOMAIR than %BF.

Conclusions

In obese middle-school children, both %BF and VO2max/kgLBM are independent predictors of FI levels. The relationship between CVF and FI levels was significant in both sexes but was particularly profound and stronger than %BF in males. Efforts to reduce risk of type 2 diabetes mellitus in an increasingly obese child population should include exercise intervention sustained enough to improve CVF.

Section snippets

Methods

Children (n = 106) at a single middle school with a body mass index above the 95th percentile for age participated in this study. Over a 24-month period, each participant underwent testing at the University of Wisconsin Exercise Science Laboratory before and at the conclusion of the 9-month school year during a single visit after an overnight fast, supervised by the same investigators. The procedures were approved by the Human Subjects Committee, and informed written consent was obtained before

Results

Patient characteristics are presented in the Table as mean ± SD. At study enrollment, mean age of the study participants was 12.8 ± 1.4 years, and 55% of the subjects were female. The mean body mass index (BMI) was 30.8 ± 5.9 (males 31.7 ± 6.9, females 30.1 ± 5.0; P = .237), and mean percent body fat (%BF) was 35.8 ± 5.5 (males 36.0 ± 6.3, females 35.6 ± 4.9; P = .462). Mean measurement of Vo2max/kgLBM at study initiation was 62.0 ± 16.4 mL/kg/min for females, 68.3 ± 16.4 mL/kg/min for males (P

Discussion

This study shows that, like adults, cardiovascular fitness is an equal, perhaps even more important predictor of insulin sensitivity than is fatness in children. Differences in the interactions between CVF and %BF with sex have been noted previously.16 Our data suggest that the adverse effects on FI levels were most profound in males with high %BF and low CVF. In one prior study of older adolescents, when CVF (assessed by sub-maximal Vo2 consumption) and %BF were analyzed together, for boys,

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  • Cited by (0)

    Supported by grants from Genentech Center for Clinical Research and the UW Sports Medicine Classic Fund.

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