The bearing of diverse patterns of diet on growth and menarche in four ethnic groups of South African girls.

Anthropemetric and development studies were made on 4390 black rural and urban, coloured, Indian and white school girls of 6-17 years and a 24-h dietary recall recorded on subsamples. Mean weights and heights of non-white were lower at all ages than those of white girls. Prevalences of obesity (greater than or equal to 120% weight-for-height), were higher in black and coloured than in Indian and white girls, but mean percentage body fat was not significantly different at 17 years. Growth attained was in response to very different dietary patterns. However, this did not delay breast development, which occurred at much the same time in all groups. However, menstruation was delayed in black compared with coloured, Indian and white girls. Although breast development was present in all at 14 years, proportions (%) menstruating differed: 33 rural and urban black; 84 coloured; 93 Indian; 97 white. in non-menstruating girls of 8 years of age all had mean fat greater than 17% (the expected level of menstruation) and, except in black rural and coloured girls, this was greater than 22%, the critical level for regular ovulation. These studies throw doubt on the nutritional components as being wholly responsible for the delay of menarche, as breast development, the earliest sign of puberty in girls, is not delayed despite marked dietary differences. The emergence of obesity without dietary intervention in the 'poorest' of adolescent girls, further questions this hypothesis.