Effects of low-protein diet on carbohydrate metabolism and energy expenditure

Low-protein diets (LPD), which are prescribed for uremic patients to slow the progression of chronic renal failure, theoretically may exacerbate disorders of carbohydrate metabolism that are frequently observed in these patients because increased carbohydrate rations are required to maintain a sufficient caloric intake. No such exacerbation actually occurs. Glucose tolerance has been shown to improve after 3 months of a diet affording .3 g protein/kg body weight supplemented with essential amino acids and ketoanalogs with carbohydrates accounting for 67% of the total energy intake. Hyperinsulinemic euglycemic clamp studies show that this amelioration is linked with an increase in insulin sensitivity, which is also observed in uremic diabetic patients on this diet. The improvement in glucose tolerance involves the insulin sensitivity of endogenous glucose production, glucose oxidative disposal, and its nonoxidative disposal. Besides these effects, LPD increases the metabolic clearance rate of insulin and causes blood insulin levels to decrease. LPD's low acid load and phosphorus content, the reduced synthesis of uremic toxins derived from alimentary protein, or both may explain these effects, which are indirectly protective against atherosclerosis. However, the significant increase in resting energy production after 3 months on LPD justifies strict monitoring of nutritional status and caloric intake.