We aimed to develop cut -points for directly measured peak oxygen uptake (VO2peak ) to identify boys and girls at increased cardiometabolic risk using different scaling methods to control for body size and composition. Altogether 352 children (186 boys, 166 girls) aged 9 – 11 years were included in the analyses. We measured VO2peak directly during a maximal cycle ergometer exercise test and lean body mass (LM) by bioelectrical impedance. We computed a sex - and age -specific cardiometabolic risk score (CRS) by summing important cardiometabolic risk factors and defined increased cardiometabolic risk as >1 standard deviation above the mean of CRS. Receiver operating characteristics curves were used to detect

O2peak cut -points for increased cardiometabolic risk. Boys with

VO2peak <45.8 mL ·kg body mass (BM) - 1 ·min - 1 (95% confidence interval [CI] = 45.1 to 54.6, area under the curve [AU C ] = 0.86, p<0.001) and <63.2 mL ·kg L M - 1 ·min - 1 (95% CI = 52.4 to 67.5, AUC = 0.65, p=0.006) had an increased CRS. Girls with

VO2peak <44.1 mL ·kg BM - 1 ·min - 1 (95% CI = 44.0 to 58.6, AUC = 0.67, p=0.013) had an increased CRS.

2peak scaled by BM -0.49 and LM -0.77 derived from log -linear allometric modelling poorly predicted increased cardiometabolic risk in boys and girls. In conclusion, directly measured

VO2peak <45.8 mL ·kg BM - 1 ·min - 1 among boys and <44.1 mL·kg BM - 1 ·min -1 among girls were cut -points to identify those at increased cardiometabolic risk . Appropriately controlling for body size and composition reduced the ability of cardiorespiratory fitness to identify children at increased cardiometabolic risk.