Adolescent growth in weight and its relation to menarche in contemporary American girls.

Weight measurements at frequent intervals, from age six to adulthood, of 248 contemporary middle-class American girls were fitted to a mathematical model (Preece and Baines 1978). The results are used to examine weight and weight velocity at specified ages, the characteristics of the weight growth spurt and the relation of this spurt to menarche. These statistics are compared with previously complied height statistics for the same girls. Although the data of all 248 girls were readily fitted, no usable spurt take-off ages were found for 41 girls. Calculations, therefore, were made separately for two subsets: principal subset A (207) and variant subset B (41). The values (subset A) for weight at specified ages and at critical points of the adolescent growth spurt agree well with comparable US and Western European data. Comparing weight spurt (subset A) with height spurt, the weight spurt takes off earlier, peaks and ends later; adult weight is reached much later. The Preece-Baines model lacks a component for analysing the mid-growth spurt. Therefore, for some children, the model makes a too-early estimate of age at adolescent spurt take-off (and other dependent variables). This may account for the unrealistic take-off ages of girls in subset B, although these girls are also significantly younger and lighter than subset A girls at spurt peak and are also younger at menarche. While certain differences between the two subsets may be mathematical distortions caused by the Preece-Baines model, others may be real.