Body mass index and age at menarche in an adolescent clinic population.

Body fatness as a determinant of menarche has been studied extensively, but limited to underweight females. Adolescent female patients were measured and interviewed. Subjects were divided into three groups based on body mass index (BMI) standard deviation score (SDS). Average age at menarche was 11.87 +/- 1.1 years in the obese group, 12.14 +/- 0.9 years in the overweight group, and 12.20 +/- 1.3 years in the normal weight group. Pearson correlation factor between BMI SDS and age at menarche was -0.24 (p < 0.01). These findings suggest an important role of increased body fatness on menarche that extends beyond underweight girls.