Height velocity, body fat and menarcheal age of Indian girls.

OBJECTIVE: To understand the onset of menarche in relation to changes in physical measurements that take place during adolescence, especially the changes in height velocity and changes in body fat.
DESIGN: Adolescent girls in the 9-16 year age group were observed longitudinally every six months for a period of two years.
SETTING: Girls from schools catering to urban high socio-economic class (HSE, n = 135) and those catering to low socio-economic class (LSE, n = 398) were evaluated.
METHODS: Six monthly measurements of weight, height and triceps skinfold thickness (TSFT) were done. Menarcheal age was recorded by recall method for the girls who were menstruating at the beginning of the study and prospectively for girls whose onset was after the initiation of the study. Body fat (%) was estimated using weight, height and TSFT.
RESULTS: The girls from LSE not only had lower attained weight, height, skinfold thickness at triceps and body fat but also had a significant difference (p < 0.05) in menarcheal age (15.4 yr) as compared to girls from HSE (12.1 yr). Although social class differences delayed the occurrence of the event by chronological age, the time between peak height velocity (PHV) and onset of menarche remained similar (1.5 yr) irrespective of social class. The mean weight at menarche, at group level (but not at individual level), was around 38 kg in both socio-economic classes, irrespective of age at onset. Further menarche represented the point of maximum deceleration in height velocity and maximum acceleration in body fat in both social classes.
CONCLUSION: Our data indicated a partial support for critical weight hypothesis and suggested that these limits vary from community to community. The analysis revealed that rather than absolute values of weight, height and body fat, changes in these measurements are of significance with regard to onset of menarche.