Thirty-three patients with type 2 diabetes mellitus (16 men, 17 women) were divided into 3 groups based on urinary excretion of albumin (U-Alb)--group A: U-Alb < 30 mg/d; group B: 30 mg/d < or = U-Alb < or = 300 mg/d; and group C: 300 mg/d < U-Alb. Serum creatinine levels were lower than 2.0 mg/dL in all the subjects. There was no difference in age, sex, therapy, body weight, body mass index (BMI), lean body mass (LBM), or hemoglobin A(1c) (HbA(1c)) levels among the 3 groups. Resting metabolic rate (RMR) (kJ/h/m(2)) and adjusted RMR for lean body mass (kJ/h/m(2)) were significantly increased in group C compared with groups A and B. Hb concentrations, serum albumin levels, and creatinine clearance were much lower in group C than in groups A and B (P < .001). There were no difference in serum urea nitrogen, total cholesterol, cholinesterase and free thyroxine, or plasma insulin-like growth factor I (IGF-I) levels among the 3 groups. Linear regression analysis revealed an inverse correlation between RMR and serum albumin levels, correlation between RMR and U-Alb, and inverse correlation between RMR and Hb concentrations, respectively, in these patients. In conclusion, RMR in diabetic patients correlated directly with U-Alb and inversely with serum albumin and Hb concentration. These findings suggest that RMR is related with urinary albumin loss and anemia in patients with type 2 diabetes mellitus accompanied by diabetic nephropathy.