Puberty begins with a characteristic subcutaneous body fat mass in each sex.

OBJECTIVE: To observe whether there exists a characteristic body fat mass at pubertal onset. DESIGN: Longitudinal clinical follow-up (between ages of 10 and 15 y) with an annual visit in a sample of 469 children. They were grouped according to age of purbertal onset: boys with pubertal onset at the ages of 11 (n=59), 12 (n=88), 13 n=89) and 14 y (n=46), and girls with pubertal onset at the age of 10 (n=68), 11 (n=66), 12 (n=37) and 13 (n=16). METHODS: Height, weight, upper arm circumference and four skinfold thicknesses were recorded annually. In boys testicular volume index was measured, and genital development was assessed on the Tanner scale; in girls mammary development was measured also using the Tanner scale. The sum of four skinfolds, body mass index, upper arm fat estimate and percentage body fat were calculated. RESULTS: Boys presented a positive relation between the age of pubertal onset and body mass index (P<0.001), which was not observed in girls. Body mass index thus varied according to the onset of puberty in boys (P<0.001), but not in girls. The sum of four skinfolds, the upper arm fat estimate index and the percentage of body fat mass did not differ according to age of pubertal onset either in girls (P=NS) or in boys (P=NS). The characteristic adiposity of the puberty onset is progressively acquired during the previous years in all the groups. CONCLUSIONS: Puberty seems to begin with a characteristic subcutaneous body fat mass that is independent of the age of onset. This study supports the hypothesis of a close link between maturation and the development of an energy store in the form of adipose tissue in both sexes.