Reference:
Phinney, S.D., Bistrian, B.R., Wolfe, R.R., et al., "The Human Metabolic Response to Chronic Ketosis Without Caloric Restriction: Physical and Biochemical Adaptation," Metabolism, 32(8), 1983, pages 757-768.
Summary:
Many studies that have analyzed ketogenic diets looked at the effects of ketogenic diets in conjunction with caloric restriction. Individuals reduced their carbohydrate intake while at the same time reducing their total amount of calories consumed. This study sought to evaluate the effects of a ketogenic diet on individuals taking in sufficient calories to ensure weight maintenance. Thus, weight loss was not the purpose of this study. Nine lean healthy men were selected for this 35-day project. Based on their age, height, weight and activity level, a diet was selected for each individual that sought to provide enough calories to meet daily needs. If subjects took in the same amount of calories that they burned, theoretically, neither weight loss nor weight gain should occur. For seven days, subjects were given a mixed diet comprised of 1.75 grams of protein per kilogram of body weight, with the remainder of calories divided as 33% fat and 67% carbohydrate. On the eighth day, subjects were switched to a diet consisting of the same amount of calories and protein, but with fewer than 20 grams of carbohydrate, which they followed for four weeks. Therefore, 83% to 85% of total calories provided came from fat. Researchers analyzed body composition, liver function, kidney function, blood lipids, blood glucose and cardiac function in all subjects upon completion of the study. As expected, there were no dramatic changes in weight among the subjects. However, there was an average gain of close to one pound of muscle mass in each individual. Researchers noted no significant change in bilirubin levels over the five weeks of the study, demonstrating normal liver function. There was a slight, but not significant, decrease in triglyceride levels, as well as a significant decrease in blood glucose levels. Kidney function proved normal with no evidence of kidney stone formation in any subject during or for six months after the study. Subjects also had normal cardiac function according to weekly EKG screens. All subjects did experience a significant increase in total cholesterol levels. Researchers attributed this to diet design. Subjects were allowed to select from a number of meals. Depending on the meal choice, the daily cholesterol intake may have approached 2 grams for some subjects. In addition, the diet was virtually fiber-free. The researchers concluded that the ketogenic diet was well tolerated by lean, healthy male subjects and caused no changes in heart, kidney or liver function. Although it was not measured directly,it was presumed that there was a major shift from glucose to ketone body oxidation by the brain,as occurs in total fasting.Another point of interest was that ketosis was not accompanied by acidosis.
Commentary:
The findings of this study can be applied to the Atkins Principles of Good Health, Disease Prevention and Weight Maintenance. Individuals in this study lost body fat while gaining muscle mass, thus no change in weight was noted. Therefore, if weight loss is not an individual's goal, simply consuming slightly more calories from fat ensures weight maintenance while at the same time allowing for favorable adaptations in body composition. A low-carbohydrate diet had no deleterious effect on kidney, liver or heart function in subjects and also lowered blood glucose levels. Low blood glucose levels ensure low insulin levels in the body. If individuals can maintain low insulin levels, they reduce their risks for adult onset diabetes, obesity and other diseases related to high insulin levels.
