Some Metabolic Changes Induced by Low Carbohydrate Diets

Abstract

Both patients of normal weight and those with significant obesity were studied under the controlled circumstances of the Clinical Research Center on diets rigidly restricted in carbohydrate content and containing varying levels of protein and fat. The men of normal weight, when receiving a low-carbohydrate diet at a caloric level sufficient to maintain weight, exhibited significant elevations of blood lipid levels, particularly of cholesterol, and also developed moderate elevations of the blood urea nitrogen. Under circumstances of an adequate caloric intake, no significant elevations of uric acid or ketone bodies were noted. Obese females, on the other hand, when given a 1,200-cal carbohydrate-restricted diet, exhibited a weight loss commensurate with their caloric intake and activity. Significant hyperuricemia developed which may have been exaggerated by a concomitant excretion of ketone bodies in the urine, and this may reflect a competition at a common site in the renal tubule. While cholesterol levels fell in the initial phase of weight reduction, they tended to return to the initial level with the passage of time. The basis of a sound weight reduction program should be based on nutritional education with respect to food and its use in achieving caloric balance and on the need for regular exercise and physical activity. Emphasis should focus on the need for a long persistent effort in this most difficult problem. Calories still count —and it would seem that the most desirable metabolic mixture at a reduced calorie level would be the one that would represent all the basic categories of nutritional elements and provide a balanced contribution of all essential nutrients. The advocates of severely restricted carbohydrate diets must consider and share the responsibility related to the increased hazards of such diets.