Adiponectin (Ad) is reported to reduce insulin resistance in metabolic syndrome. The relation between the polymorphism of Ad (t45 g), biochemical indices including Ad and insulin concentrations, and food intake was examined, since the g/g homozygotes are known to be diabetes-prone. Subjects were 45 women (68.87 +/- 7.74 years old) who received preventive intervention in our nutrition clinic. Their food intake was estimated by the three day dietary record, and the blood was taken for genetic and biochemical analyses. Polymerase chain reaction and RFLP of Ad-DNA revealed the wild type (t/t = 51%), heterozygotes (t/g = 41%) and mutant homozygotes (g/g = 9%). Concentrations of total and high molecular weight Ad (12-18mers, HMW-Ad) were determined by ELISA. The project was approved by the ethics committee of our university and by the written agreement of the subject. Serum insulin concentration was negatively correlated with HMW-Ad (y = -0.802 + 11.7, P = .006), but not correlated with total Ad. HMW-Ad in the g/g homozygotes (1.18 +/- 1.28 microg/ml) was significantly (P = .024) lower than that in both wild type (t/t, 4.07 +/- 2.96 microg/ml) and heterozygotes (t/g, 2.23 +/- 1.90 microg/ml). The concentrations of fasting plasma glucose (average = 157.5 +/- 49.4 mg/dl) and HbAlc (average = 7.3 +/- 1.7%) in g/g were significantly (P < .001, in any combination) higher than those in both t/t and t/g. HMW-Ad were negatively correlated with intakes of both carbohydrate (group I food of Ministry of Health, Welfare and Labor) and sugar. The intakes of carbohydrate and sugar were not different among t/t, t/g and g/g groups. Although g/g homozygotes are diabetes prone, improvement of the insulin resistance by restricting the intakes of both carbohydrate-rich foods and cane sugar may be easier in g/g than in t/g and t/t.