A Review of Low-carbohydrate Ketogenic Diets Eric C.Westman,MD,MHS,John Mavropoulos,MPH, William S.Yancy,Jr.,MD,MHS,and Jeff S.Volek,PhD,RD Current Atherosclerosis Reports 2003
Introduction Obesity has been implicated as the second leading preventable cause of death in the United States, and studies support that intentional weight loss leads to a reduction in overall mortality [1,2]. In response to the emerging epidemic of obesity, there has been a renewal of interest in alternative diets. Given the current unfavorable trends with conventional approaches, a reconsideration of previously unevaluated alternative diet therapies is not unreasonable. Based on lay-press book sales, the most popular alternative weight-loss diet is the very low-carbohydrate diet. Diets that limit carbohydrate intake have been called “low-carbohydrate,” “very-low-carbohydrate,” “high-protein,” “high-fat,” and “ketogenic.” Presently, there is no consensus on a precise quantitative definition for a low-carbohydrate diet. A lowcarbohydrate diet may or may not be a “high-protein diet” depending upon the food choice and caloric intake. For the purpose of this review, we define a “low-carbohydrate ketogenic diet” (LCKD) as daily consumption of fewer than 50 g of carbohydrate, regardless of fat, protein, or caloric intake.
Conclusions In controlled trials, the LCKD has been demonstrated to lead to weight loss and improvements in fasting triglycerides, HDL cholesterol, and cholesterol/HDL ratio over a 6-month period. Clinical trials assessing the long-term safety and effectiveness of the LCKD are needed. The LCKD needs to be evaluated not only for obesity, but also for conditions that have a theoretical basis for improvement by a reduction in dietary carbohydrate and a shift from a glucocentric to adipocentric metabolism. Although the basic physiology of an LCKD resembles the state of prolonged fasting, there are key differences such that basic studies regarding LCKD physiology are urgently needed. Fundamental questions regarding fuel utilization and the regulation of gluconeogenesis and ketogenesis in the presence of protein and fat intake need to be addressed. The cultural example of the Inuit demonstrates the remarkable adaptability of the human organism to withstand extremes of macronutrient intake, necessitating the questioning of whether dietary carbohydrate is required for human function . Because these findings from clinical trials have been counterintuitive, clinical research strongly suggests that studying the LCKD may lead to unexpected advances in molecular cell biology and clinical therapeutics.