Dietary energy requirements were evaluated during 16 studies that were carried out in six clinically stable nondialyzed chronically uremic patients who lived in a clinical research center and were fed diets providing 45, 35, 25 or 15 kcal/kg/day. Each diet was fed for 23.7 +/- 5.7 SD days and provided about 0.55 to 0.60 g protein/kg/day. Nitrogen balance after equilibration and adjusted for changes in body urea nitrogen, and change in body weight each correlated directly with energy intake. Correcting for estimated unmeasured nitrogen losses of about 0.58 g/day, nitrogen balance was negative in one of four patients fed 45 kcal/kg/day, one of five patients receiving 35 kcal/kg/day, three of five patients ingesting 25 kcal/kg/day and both patients fed 15 kcal/kg/day. The urea nitrogen appearance (UNA), the UNA divided by nitrogen intake, and several plasma amino acids, determined after an overnight fast, each correlated inversely with dietary energy intake. Resting energy expenditure measured by indirect calorimetry did not differ from normal and averaged 0.012 +/- 0.0033 kcal/kg/min with the different diets. These observations suggest that although some clinically stable nondialyzed chronically uremic patients ingesting 0.55 to 0.60 g protein/kg/day may maintain nitrogen balance with energy intakes below 30 kcal/kg/day, a dietary intake providing approximately 35 kcal/kg/day may be more likely to maintain neutral or positive nitrogen balance, maintain or increase body mass, and reduce net urea generation.

Although nondialyzed, chronically uremic patients and patients undergoing maintenance hemodialysis often show evidence for wasting and calorie malnutrition and have low dietary energy intakes, their energy expenditure has never been systematically evaluated. It is possible that low energy intakes are an adaptive response to reduced energy needs; alternatively, energy expenditure could be normal or high and the low energy intakes would be inappropriate. Energy expenditure was therefore measured by indirect calorimetry in 12 normal individuals, 10 nondialyzed patients with chronic renal failure, and 16 patients undergoing maintenance hemodialysis. Energy expenditure was measured in the resting state, during quiet sitting, during controlled exercise on an exercise bicycle, and for four hours after ingestion of a test meal. Resting energy expenditure (kcal/min/1.73 m2) in the normal subjects, chronically uremic patients and hemodialysis patients was, respectively, 0.94 +/- 0.24 (SD), 0.91 +/- 0.20, and 0.97 +/- 0.10. There was also no difference among the three groups in energy expenditure during sitting, exercise, or the postprandial state. Within each group, energy expenditure during resting and sitting was directly correlated. During bicycling, energy expenditure was directly correlated with work performed, and the regression equation for this relationship was similar in each of the three groups. These findings suggest that for a given physical activity, energy expenditure in nondialyzed, chronically uremic patients and maintenance hemodialysis patients is not different from normal. The low energy intakes of many of these patients may be inadequate for their needs.