2 shown to be less discriminant than fatness as suggested by a recent report [21]; we took into account the gender and the pubertal development of adolescents, owing to the changes that occur in their lifestyle and hormonal status. 2. Subjects and Methods The study is part of a research protocol on the genetics of child obesity, which has been approved by the Ethics Committee of the Hoˆ tel Dieu Hospital (Paris); a written consent to the inclusion in the study was given by each child’s parents and by adolescents themselves [22]. Subjects were children and adolescents attending the specialized clinic of University Hospital of Caen; they were routinely screened before treatment. The clinical examination of children was performed by the same clinician. They were all apparently healthy with no obvious endocrine disease. Pubertal stage was assessed according to Tanner criteria [23]. Weight was assessed with an electronic beam balance; height was measured twice by the same examiner to the nearest 0.5 cm. Body mass index (BMI) was calculated (kg/m2). Patients were considered as overweight when their BMI was over 2 SD of the available French charts [24], which ﬁt better with the local population than the IOTF charts; data were also compared with IOTF cut oﬀ points [25]. Blood pressure (BP) was measured by an automatic device on a sitting patient, at least twice, at the end of a consultation (Agilent A1; Agilent 91745 Massy France). Blood sample was drawn after an overnight fast, for mea- surements of plasma glucose, insulin, triglycerides, HDL and LDL cholesterol, alanine aminotransferase (ALT), aspartate aminotransferase (AST), sedimentation rate and ﬁbrinogen. Homeostasis model assessment-insulin resistance (HOMA- IR) was calculated as a measure of insulin resistance (insulin (mU/L) ∗ plasma glucose (mmol/L)/22.5). Body composition (total and relative (%) fat and fat- free mass) was measured by X-ray absorptiometry (DEXA) (HOLOGIC QDR-4500 A) [26]. VO2Max was measured by a previously validated proto- col reported [26]; it was adapted from Achten [27]; the use of this graded exercise to exhaustion gives an exact value of the peak VO2 [26, 27]; subjects performed a graded exercise on a bicycle ergometer (ERGOLINE 500, Bosch) linked to a gas analyzer (Ergocard SCHILLER). Before the test, the children were given several minutes to familiarise themselves with the ergometer and to adapt to the valve/mouthpiece. The subjects warmed up for 5 minutes at 0 W. The ﬁrst step was ﬁxed at 30 W with a rectangular progression of 20 W every 3 minutes 30 seconds, until exhaustion. 2.1. Statistical Analysis. Results were expressed as mean ± 1 SD; statistical analysis used univariate regression analysis between VO2max and anthropometric and biologic data; multivariate analyses performed on each gender; they used age and % fat mass as covariates of VO2max. Tanner stage was also tested as covariate. The level of signiﬁcance was set at P < .05. N Age Tanner Weight Height BMI z Score BMI Overweight (IOTF cut oﬀ points) Obesity (IOTF cut oﬀ points) Fat Free Mass Fat Mass VO2 max Systolic BP Diastolic BP Fasting Glucose Fasting Insulin HOMA-IR HDL Cholesterol LDL Cholesterol Triglycerides AST ALT Sedimentation rate Fibrinogen 3. Results International Journal of Pediatrics Table 1: Descriptive data. Unit Years k/m2 k m % % % % MmHg MmHg mmol/L mU/L Mmol/L mmol/L mmol/L IU/L IU/L g/L mL O2/k/min Girls X 135 11.9 3.0 62.4 1.52 26.7 5.1 47 53 56.6 40.6 25.5 116 61 4.7 10.4 2.1 1.5 2.8 0.8 23 24 13 3.6 SD 2.3 1.8 16.8 0.11 4.5 2.5 6.4 6.4 5.1 19 12 0.4 5.4 1.1 0.4 0.9 0.4 8 7 6 0.8 Boys x 106 12.1 2.0 69.0 1.55 28.1 5.8 37 63 57.6 39.3 27.9 120 65 4.9 10.9 2.4 1.4 2.7 0.9 24 28 12 3.6 SD 2.3 1.3 21.2 0.12 5.8 2.9 6.8 6.6 6.1 13 10 0.4 7.2 1.7 0.3 1.3 0.5 7 17 7 0.7 241 children were studied (135 girls), aged 11.9 ± 2.2 years (x ± SD), range: 6.2 ± 17.9; their BMI z score was 5.4 ± 2.7. Descriptive data are given in Table 1. Univariate regressions (Table 2) displayed signiﬁcant relationships between VO2max and age, pubertal develop- ment, BMI, body composition parameters, insulin and HOMA-IR, lipids and ALT (≤0.02), and inﬂammation parameters (P ≤ .0005). Table 3 shows the results of multivariate regression analysis. Since Tanner stage did not enter in any model, it was discarded from analysis. For girls, VO2 max remained signiﬁcantly associated with insulin (P = .001), HOMA- IR (P = .005), and ALT (P = .012); a relationship was displayed between ﬁbrinogen and age and % fat mass (P = .008); for boys, relationships were found between VO2max and diastolic BP and triglycerides; independent associations were also found between age and insulin, HOMA-IR, and HDL cholesterol; ﬁbrinogen and sedimentation rate were related (P ≤ .004) with %FM.