In adults, gender and obesity play significant roles in the regulation of blood pressure (BP). This study investigated the effects of gender and body mass index (BMI) on BP during adolescence.

A cross-sectional and longitudinal study involving 6838 students under twenty years old (median, eighteen years old; male, 4624; female, 2214) at Osaka University visited the Healthcare Center for their matriculation health examination from April to May in the years 2008, 2009, and 2010, and re-visited the Healthcare Center for their student health examination from May to June in the years 2011, 2012, and 2013.

Height, body weight, and BP were measured in students both on and 3 years after admission to Osaka University.

On admission, the slope of the regression line for BMI and systolic BP (SBP) in non-underweight students was significantly different between genders. SBP and diastolic BP (DBP) increased in both genders during the observation period. Among male students who had a normal BMI on admission, those who had an increase in BMI of over 4% during the observation period showed a greater increase in SBP than those who had a change in BMI of −4% to 4%. On the other hand, female students showed no change in BP with the increase in BMI.

The magnitude of BP elevation with increased BMI was associated with gender during adolescence. This may be a cause of the higher prevalence of hypertension in adult males.