Although, weight loss is associated with improved glycemic control in diabetic patients, the relationships between patient weight, daily energy intake (EI), and glycemic or other control status have been poorly investigated. Baseline characteristics of the Japan Diabetes Complications Study, a representative cohort of Japanese diabetic patients, were used for quartile analysis stratified according to patient body mass index (BMI) and EI. Despite a 1.4-fold discrepancy in BMI between the highest and the lowest quartiles, no significant linear trend in HbA(1C) levels or EI between quartiles was seen, although, waist/hip ratio, blood pressure, total cholesterol and triglycerides increased and HDL cholesterol decreased with the increase in BMI. Quartile analysis, according to EI, revealed a 1.8-fold elevation in EI between the lowest and the highest quartile. Nevertheless, the differences in patient BMI between the lowest and the highest quartile were no more than 3% and there were no significant linear trends among the four quartiles in most parameters including HbA(1C), blood pressure, serum lipids. These results revealed only very limited cross-sectional correlations among BMI, EI and other parameters suggesting that it is necessary to consider much wider variations in ideal weight and optimal dietary prescription when making assessments of diabetic patients.