Mean (± SD) characteristics of the subjects at baseline measurement.

aSignificantly different from underweight boys;bsignificantly different from normal weight boys;csignificantly different from overweight boys;dsignificantly different from obese boys (PBiological age is years from APHV (age at peak height velocity); BMI, body mass index; TB BMD, total body bone mineral density; FN BMD, femoral neck bone mineral density; LS BMD, lumbar spine bone mineral density; SED, sedentary time; MVPA, moderate and vigorous physical activity.Mean (± SD) characteristics of the subjects at baseline measurement.