Background:Previous reports have revealed that fatty liver involving obesity is closely related to insulin resistance or hyperinsulinemia in adulthood. This study investigates the importance of hyperinsulinemia in obese children with fatty liver.Methods:The subjects were 228 obese children 6 to 15 years old in Niigata Prefecture, Japan. The serum level of glutamic pyruvic transaminase (GPT) was evaluated as an indicator of fatty liver. The effects of their percent obesity (percent over ideal body weight), Rohrer index (g/cm3), skinfold thickness, percent body fat measured by bioelectrical impedance analysis, total cholesterol (TC), high-density lipoprotein cholesterol, triglyceride (TG), blood glucose, and immuno-reactive insulin (IRI) on GPT were evaluated using regression analyses.Results:The incidence of fatty liver (GPT over 35 IU/I) was 24.1% in this study. In simple regression analyses, percent obesity, Rohrer index, skinfold thickness, TC, TG, blood glucose, and IRI correlated positively with GPT (p < 0.05). In stepwise regression analysis including these seven variables, the predictive equation for GPT as a function of IRI alone accounted for 24.2% of the total variance of GPT. The addition of TC alone, and TC and percent obesity together increased the coefficients of determination to 28.4% and 29.9%, respectively. Rohrer index, skinfold thickness, Tg, and blood glucose were not taken as related variables with GPT.Conclusion:Hyperinsulinemia is an important contributor to the development of fatty liver, apparently more than anthropometric data, blood glucose, or serum lipids in childhood obesity.