SummaryA 10-year longitudinal study was conducted on 26 prepubescent youngsters who had undergone successful weight reduction. Their ages ranged from 2 to 10 years when the study began. In all subjects, weight reduction proceeded only by a decrease in adipose cell size (from 0.62 ± 0.02 to 0.46 ± 0.02 μg lipid per cell) and resulted in a corresponding 33% decrease (from 177 ± 6 to 144 ± 5%) in percent ideal body weights. Cell numbers did not change appreciably during the period of weight loss (29.4 ± 2.6versus28.7 ± 2.3 × 109total adipocytes). Three years after the start of the study, 14 of 20 youngsters had maintained their reduced percent ideal body weights, including eight who remained below 130% ideal body weight. Ten years later, only four remained below 130% ideal body weight. AH four children had total adipose cell numbers below 20 × 109total adipocytes at the start of the weight reduction program, a value below the lower limit for adult normal weight subjects. Thirteen other children have maintained or decreased their initial percent ideal weights. The remaining nine youngsters have further increased their percent ideal body weights.In vitrometabolic studies of the patient's adipocytes revealed a >50% depression of epinephrine-stimulated lipolysis pre- and immediately postweight reduction; this decrease persisted for the entire period of study, irrespective of the maintenance of a normal percent ideal body weight. At the same time, normal 150% increases in thein vitroproduction of14CO2from [1-14C]glucose in the presence of insulin occurred.SpeculationMaintaining weight reduction long term is generally unsuccessful except in a small minority of very young obese children. Therefore, if the prevalence of obesity and its associated diseases are to be decreased, very early identification of at-risk youngsters is important. Specific enzymatic and metabolic alterations in these children,e.g., depression ofin vitroepinephrine-stimulated lipolysis, appear to be useful for early identification of susceptible individuals. In addition, this study indicates that factors such as genetics and gestation may lay the groundwork for the future development of increased adiposity.