Body composition development of adolescent white females: the Penn State Young Women's Health Study.

OBJECTIVE

To obtain simultaneous and longitudinal measures of height, weight, total body bone mineral content, total body bone mineral density, percentage of body fat, lean body mass, and body mass index in healthy white females between the ages of 11 and 18 years.

DESIGN

A longitudinal, observational study.

SETTING

University medical center in a small city.

STUDY

PARTICIPANTS

At initiation in 1990, 112 premenarchal, healthy girls were enrolled. Results presented in this report are based on measurements made on the 82 participants who remained in the study in 1996 and for whom we had comprehensive measurements.

INTERVENTIONS: None.

MAIN OUTCOME MEASURES: Dual-energy x-ray absorptiometry was used to obtain measurements of total body bone mineral content, total body bone mineral density, percentage of body fat, and lean body mass every 6 months for the first 4 years of the study and yearly thereafter.

RESULTS

The mean age for peak velocity and peak accumulation for each measurement was as follows: height, 11 1/2 and 17 1/2 years, respectively; weight, 11 1/2 and 17 1/2 years; body mass index, 11 1/2 and 17 1/2 years; percentage of body fat, 11 1/2 and 13 1/2 years; lean body mass, 12 and 17 1/2 years; total body bone mineral content, 13 1/2 and 17 1/2 years; and total body bone mineral density, 13 1/2 and 17 1/2 years.

CONCLUSIONS

Among a healthy population of white females, the age of peak velocities for height, weight, body fat, and lean body mass occur at 11 1/2 to 12 years. Thus, peak soft-tissue velocities precede hard-tissue velocities by about 2 years, with peak accumulation of all tissue components being reached, on average, by age 17 1/2 years.