Patients with type 2 diabetes mellitus (DM), obesity, and chronic kidney disease (CKD) are generally physically inactive and may benefit from exercise. Our objective was to determine the effects of structured exercise on physical fitness, kidney function, endothelial function, inflammation, and body composition in such patients. In this randomized, controlled trial, 36 male patients (age 49-81) were randomly assigned to exercise + diet management (n = 18) or diet alone (n = 18). Participants were eligible if they had type 2 DM, body mass index >30 kg/m2, CKD stages 2-4, and persistent proteinuria (>200 mg/g creatinine for >3 months). The exercise intervention was a 12-week (3 days per week) program of aerobic and resistance training followed by 40 weeks of home exercise. The primary outcome measure was change from baseline in urine protein to creatinine ratio (UPCR) at 12 and 52 weeks. Thirty-two participants completed the study (14 exercise + diet, 18 diet-alone group). The change from baseline in UPCR was slightly greater in the diet-alone group at 12 weeks but not at 52 weeks. Changes in both symptom-limited and constant-workrate treadmill times were significantly higher in the exercise + diet group at 12 weeks but not at 52 weeks. There were no significant differences in urine albumin to creatinine ratio, estimated glomerular filtration rate, endothelial function, inflammation, or body composition between the groups. In obese diabetic subjects with CKD, structured exercise improved exercise capacity but not body composition or renal function. This is a work of the US Government and is not subject to copyright protection in the USA. Foreign copyrights may apply. Published by S. Karger AG, Basel.