Early Pubertal Development and Overweight in Girls

During the last decades obesity has become more frequent in many parts of the world causing serious health problems like cardiovascular diseases, diabetes, etc. It has been postulated that during childhood critical periods exist during which obesity is developed or aggravated.1,2 One critical period is puberty. We have studied 47 healthy girls, aged 9 to 11 years. Thirty girls were normal weight (NW), and 17 overweight (> 85th percentile; OW). The study was repeated after 6, 12, and 24 months in order to follow weight development during puberty. In this contribution, only the crosssectional data from the first study are reported. Weight and height were recorded. Body composition was measured by the bioimpedance method. Tanner stages of pubertal development were evaluated by a pediatrician (A. Angst). Breast and pubertal hair development scores were averaged to yield the Tanner stage. Blood was drawn after an overnight fast, and luteinizing hormones (LH), follicle-stimulating hormone (FSH), estradiol, DHEA-S, IgF1, leptin, and insulin were measured by enzyme immunoassay. Resting metabolic rate (RMR) was measured by indirect calorimetry, using the ventilated hood system (Deltatrac®). Total energy expenditure (TEE) was measured by the double-labeled water method over a two-week period as published by our group earlier.3 Non-basal energy expenditure was calculated from the difference of TEE and RMR and served as an estimate of activity-induced thermogenesis (AIT). At the time of the first study, 60% of the NW girls were prepubertal. Twenty-two percent were in Tanner stage 1.5 and 10% in Tanner stage 2. In the OW group a lower percentage (42%) were prepubertal and a higher percentage was in stage 1.5 (43%) and stage 2 (25%). The OW group in early puberty (stage 1.5 and stage 2) were on the average 9.5 and 9.6 years old. The NW peers were on the average 10.4 and 11.2 years old. These data confirm earlier observations indicating that OW girls enter pubertal development earlier than NW girls. When LH, FSH, and estradiol were compared in NW and OW girls, no significant differences were observed in the single pubertal stages (data not shown). This confirms earlier data by Klein et al.4 Body weight and body fat data are plotted in FIGURE 1. The increase in total body fat is significantly greater in the OW group. The percentage of body fat in the NW group increases on the average from 16% in stage 1 to 17.5% in Tanner stage 2. In the OW group the percent fat rises from 25 to 33%. In agreement with these observations plasma leptin, which is produced by fat tissue rises to a significantly greater extent in OW than in NW girls (FIG. 1). Since there is good evidence (for review see ref. 5) that leptin facilitates or even triggers development of reproductive function, the higher leptin values in the OW group may be responsible for the early development of pu-