PurposeEarly timing of pubertal development is associated with worse cardiometabolic health in adulthood. We aimed to evaluate this association in 10-year-old girls and boys and clarify if it is independent of previous body mass index (BMI). MethodsPubertal development was evaluated through the Tanner scale in 4,548 children from the birth cohort Generation XXI. Data on anthropometrics, body composition, blood pressure, lipid profile, fasting plasma glucose, insulin, homeostatic model assessment–insulin resistance (HOMA-IR), and high-sensitivity C-reactive protein were collected. Bonferroni correction was applied, using an alpha of .004 for statistical significance. Regression coefficients and 99.6% confidence intervals were computed using linear regression models. ResultsGirls with a Tanner stage ≥2 presented statistically significant higher values of BMI, waist circumference (WC), waist-to-height ratio, fat mass index, blood pressure, glucose, insulin, HOMA-IR, triglycerides, and high-sensitivity C-reactive protein and lower values of high-density lipoprotein cholesterol. Boys with a Tanner stage ≥2 presented statistically significant higher values of BMI, WC, systolic blood pressure, and HOMA-IR and lower values of high-density lipoprotein cholesterol. After adjustment, including previous BMI, a Tanner stage ≥2 remained associated with BMI z-score (girls β = .41 [.32, .50]; boys β = .10 [.01, .19]) and WC (girls β = 2.64 cm [1.86, 3.43]; boys β = .81 cm [.11, 1.51]), and only in girls with waist-to-height ratio (β = .01 [.00, .01]), fat mass index (β = .31 kg/m2 [.08; .54]), glucose (β = 1.59 mg/dL [.85, 2.33]), insulin (β = 1.73 μU/mL [.68, 2.78]), and HOMA-IR (β = .40 [.16, .64]). ConclusionsIndependently of previous BMI, preteens with early puberty already had more adiposity at age 10 years. In addition, girls had higher glucose, insulin, and HOMA-IR, which may predict a worse glucose metabolism. These preteens should be a target for public health interventions.