Pubertal BMI change is an independent risk marker of cardiovascular mortality/morbidity. Previous studies demonstrated a secular trend of increased childhood BMI but it is unknown if there is a concomitant secular trend regarding pubertal BMI change. The aim of this study was to describe the trend in pubertal BMI change. We collected heights and weights before and after puberty from school health records and military conscript records for boys born every five years during 1946-1991 (n = 3650, total cohort) and calculated pubertal BMI change (young adult BMI at 20 years of age minus childhood BMI at 8 years of age) for all study participants. A secular trend of increasing pubertal BMI change during the study period was observed. The increase in pubertal BMI change (0.27 kg/m per decade 0.22; 0.32) explained 54% of the secular trend of increasing young adult BMI (0.50 kg/m per decade 0.43; 0.57). We made the novel observation that there is a secular trend of increasing pubertal BMI change. We propose that the secular trend of increasing pubertal BMI change might contribute more than the secular trend of increasing childhood BMI to the adverse cardiovascular health consequences associated with the ongoing obesity epidemic.