The relationship between body composition and onset of menarche.

Background: A late age of menarche in elite adolescent athletes is frequently attributed to low body fat/weight. If a critical body weight/fat is necessary for menarche, a reduction in the variability of these parameters would be observed at menarche compared to times before and after this event.

Aim: The study determined the variability in body mass (BM), per cent body fat (%BF) and total body fat (TBF) of girls between -2 and +2 years from menarche.

Methods: Participants were part of the Saskatchewan Pediatric Bone Mineral Accrual Study (1991-1998). Body composition was assessed using dual X-ray absorptiometry (DXA). An individual's data was retained for analysis if they had at least four DXA scans between -3 and +3 years from menarche. Values were interpolated from the cubic spline at whole years between -2 and +2 years from menarche. Coefficient of variation (CV) was used to assess variability.

Results/conclusion: Data on 61 girls were retained for analysis. The range in BM, TBF and %BF at menarche was 50.10 kg, 35050.06 g and 31.61%, respectively. Reductions in variability of body fat and weight were not apparent at menarche, which does not provide support for the hypothesis that a critical body weight/fat is required for menarche.