- To study the relationship between body mass index (BMI) and height in 20-22 year-old patients. A research questionnaire filled by a representative sample of military personnel upon discharge from service was analyzed. At the same time, weight and height were measured, and BMI was calculated (BMI = weight (Kg)/height(2)(m(2))). There were 35,951 participants in the study, including 16204 females and 19747 males. There was a positive correlation between BMI and height in men (regression slope = 0.00717, r = 0.015, p = 0.03), while the correlation was negative in women (regression slope = -0.02811, r = -0.05, p < 0.0001). In multiple regression analysis, when BMI was used as the dependent variable and height, gender, ethnic origin, smoking, oral contraceptive use, and level of recreational exercise as the independent variables, only height, gender, and ethnic origin remained significant in the final analysis (R-square 0.0205, p < 0.0001). In young adults, BMI is affected in a subtle, but opposite manner in males and females. In males, BMI increases with increasing height, while in females, BMI decreases with increasing height.