OBJECTIVE: Malnutrition is common in patients with chronic kidney disease (CKD) who are on low-protein diets and is a powerful predictor of morbidity and mortality in CKD. Studies have shown that patients on low-protein diets often have difficulty meeting nutritional energy requirements. Our study evaluated the effects of a nonprotein calorie (NPC) supplement on renal function and nutritional status in patients on a low-protein diet. DESIGN: This was a prospective, randomized, open-label, controlled clinical trial. SUBJECTS: A total of 109 patients with CKD (men, 67%; mean age, 54.5 ± 13 years) with stage 3 to 4 disease were randomly assigned to the intervention group (n = 55) or the control group (n = 54). INTERVENTION: All participants received individualized dietary counseling aimed at achieving a daily protein intake of 0.6 to 0.8 g and a daily energy intake of 30 to 35 kcal/kg. The intervention group consumed a 200-kcal NPC supplement daily. The control group received dietary counseling only. MAIN OUTCOME MEASURE: The estimated glomerular filtration rate (eGFR) was calculated using the 4-variable Modification of Diet in Renal Disease (MDRD) Study equation. Urine protein excretion, dietary protein and energy intake, and serum levels of creatinine, urea nitrogen, cholesterol, triglycerides, and albumin were assessed at baseline, at 12 weeks, and at 24 weeks. RESULTS: Dietary protein intake and urine protein excretion levels decreased significantly in the intervention group and were significantly lower than those of the control group. In addition, serum levels of creatinine and urea nitrogen decreased significantly, and eGFR increased significantly in the intervention group compared with baseline assessments. No significant differences were observed in the control group. CONCLUSIONS: The NPC supplement improved patient adherence to the low-protein diet and reduced urine protein excretion in patients with CKD.