Ketogenic diets and physical performance. Stephen D Phinney. Abstract: Impaired physical performance is a common but not obligatory result of a low carbohydrate diet. Lessons from traditional Inuit culture indicate that time for adaptation, optimized sodium and potassium nutrition, and constraint of protein to 15–25 % of daily energy expenditure allow unimpaired endurance performance despite nutritional ketosis. Introduction: Most physicians and nutrition scientists believe that carbohydrates must constitute a major component of daily energy intake for optimum physical performance. This view is based on studies linking muscle glycogen stores to high intensity exercise and clinical experience of patients on low carbohydrate diets. The Inuit people of the Canadian and Alaskan Arctic regions were observed before their traditional dietary practices were altered, and reports imply they were physically unhampered despite a diet essentially free of identifiable carbohydrate. The origins of carbohydrate supremacy: Until the development of agriculture, human ancestors' consumption of dietary carbohydrate was opportunistic. With agriculture, societies could remain in stable locations, build permanent dwellings, and develop written language. Agriculture-based societies had advantages over hunting and fishing societies, particularly in supporting trade and transport. The science of nutrition developed in the early 20th century, with studies showing that carbohydrate was necessary for optimum human health and function. The 1939 study by Christensen and Hansen showed that high carbohydrate diets improved endurance time. The hunter's counterpoint – practical observations on ketogenic diets: High-carbohydrate diets may be more effective in short-term tests of high-intensity exercise, but there are clues in the literature that the debilitating effects of ketogenic diets are overstated. The Inuit people lived for millennia as hunters, and there are reports of Europeans living within their cultures without apparent impediment. The Schwatka expedition in 1878–80 demonstrated physical stamina during a ketogenic diet. Vilhjalmur Stefansson, a Harvard-trained anthropologist, studied the Inuit and found that they could live and function well on a diet of meat and fat. Stefansson's study showed that he and his Inuit companions survived 12 months on a meat and fat diet without signs of deficiency. Modern ketogenic diet performance studies: There was a resurgence of interest in very low calorie ketogenic diets in the 1970s, but the fatigue and cardiac dysfunction caused by this diet contrasted with the experience of arctic explorers. Studies showed that subjects on a very low calorie ketogenic diet had no decline in peak aerobic power after 6 weeks, indicating that the protein and mineral contents of the diet were adequate to preserve functional tissue. Endurance time to exhaustion was reduced after one week of the ketogenic diet but significantly increased by the 6-week time point. The results of these studies indicate that both groups experienced a lag in performance across the first week or two of carbohydrate restriction, after which both peak aerobic power and sub-maximal endurance performance were fully restored. Resolving the performance paradox: ThreeKetogenic diets and physical performance. Stephen D Phinney. Abstract: Impaired physical performance is a common but not obligatory result of a low carbohydrate diet. Lessons from traditional Inuit culture indicate that time for adaptation, optimized sodium and potassium nutrition, and constraint of protein to 15–25 % of daily energy expenditure allow unimpaired endurance performance despite nutritional ketosis. Introduction: Most physicians and nutrition scientists believe that carbohydrates must constitute a major component of daily energy intake for optimum physical performance. This view is based on studies linking muscle glycogen stores to high intensity exercise and clinical experience of patients on low carbohydrate diets. The Inuit people of the Canadian and Alaskan Arctic regions were observed before their traditional dietary practices were altered, and reports imply they were physically unhampered despite a diet essentially free of identifiable carbohydrate. The origins of carbohydrate supremacy: Until the development of agriculture, human ancestors' consumption of dietary carbohydrate was opportunistic. With agriculture, societies could remain in stable locations, build permanent dwellings, and develop written language. Agriculture-based societies had advantages over hunting and fishing societies, particularly in supporting trade and transport. The science of nutrition developed in the early 20th century, with studies showing that carbohydrate was necessary for optimum human health and function. The 1939 study by Christensen and Hansen showed that high carbohydrate diets improved endurance time. The hunter's counterpoint – practical observations on ketogenic diets: High-carbohydrate diets may be more effective in short-term tests of high-intensity exercise, but there are clues in the literature that the debilitating effects of ketogenic diets are overstated. The Inuit people lived for millennia as hunters, and there are reports of Europeans living within their cultures without apparent impediment. The Schwatka expedition in 1878–80 demonstrated physical stamina during a ketogenic diet. Vilhjalmur Stefansson, a Harvard-trained anthropologist, studied the Inuit and found that they could live and function well on a diet of meat and fat. Stefansson's study showed that he and his Inuit companions survived 12 months on a meat and fat diet without signs of deficiency. Modern ketogenic diet performance studies: There was a resurgence of interest in very low calorie ketogenic diets in the 1970s, but the fatigue and cardiac dysfunction caused by this diet contrasted with the experience of arctic explorers. Studies showed that subjects on a very low calorie ketogenic diet had no decline in peak aerobic power after 6 weeks, indicating that the protein and mineral contents of the diet were adequate to preserve functional tissue. Endurance time to exhaustion was reduced after one week of the ketogenic diet but significantly increased by the 6-week time point. The results of these studies indicate that both groups experienced a lag in performance across the first week or two of carbohydrate restriction, after which both peak aerobic power and sub-maximal endurance performance were fully restored. Resolving the performance paradox: Three