Pubertal stage and measures of adiposity in British schoolchildren.BACKGROUND:  Puberty is a critical period in the development of obesity. Body mass index (BMI), waist circumference and skin-fold thickness are used generally as estimates of body fat in children and adults. AIM:  To identify a marker of adiposity that is independent of pubertal status and determine its relationship to physical fitness in adolescence. SUBJECTS AND METHODS:  Girls (n = 147) and boys (n = 100) from year 8 in three Welsh schools self-reported Tanner stages. Anthropometric measurements of adiposity were made and aerobic fitness estimated with a 20-metre shuttle-run test. RESULTS:  Children in early and late puberty were of similar chronological age. BMI strongly correlated with height in early puberty in girls (r = 0.366, p < 0.001) and boys (r = 0.594, p < 0.001), but not in late puberty. Waist-to-height ratio adjusted for the effect of height on waist measurements; and correlated with percentage fat mass in early and late puberty in girls (r = 0.865 and r = 0.772, both p < 0.001) and boys (r = 0.868 and r = 0.877, both p < 0.001). Physical fitness score was inversely related to waist-to-height ratio, with similar regression lines in early and late puberty, in girls (r = - 0.545, p < 0.001 and r = - 0.362, p = 0.005) and boys (r = - 0.490, p < 0.001 and r = - 0.400, p = 0.003). CONCLUSION:  Pubertal status should be taken into account in adjusting weight for height in adolescents. Waist-to-height ratio is a convenient and appropriate measure of adiposity during puberty.