The article by Stephen D. Phinney explores the relationship between ketogenic diets and physical performance, challenging the common belief that a low-carbohydrate diet impairs physical performance. Drawing on historical observations from traditional Inuit culture, the author argues that with proper adaptation, optimized sodium and potassium nutrition, and controlled protein intake, individuals can maintain or even enhance endurance performance despite nutritional ketosis. Phinney reviews historical studies and personal experiences, including the Schwatka expedition and the work of Vilhjalmur Stefansson, who lived for a year on a diet consisting primarily of meat and fat. These accounts suggest that prolonged adaptation to a ketogenic diet can lead to improved physical stamina and endurance. The article also discusses modern studies conducted by Phinney and colleagues, which found that untrained and highly trained subjects experienced a delayed but full recovery in peak aerobic power and endurance performance after adapting to a ketogenic diet. The studies highlight the importance of adequate protein and mineral intake, particularly sodium and potassium, to maintain cardiovascular reserve and preserve lean body mass. Phinney concludes that while submaximal endurance performance can be sustained on a low-carbohydrate diet, careful attention to keto-adaptation time, mineral nutrition, and protein dosage is crucial. He emphasizes that therapeutic use of ketogenic diets should not restrict most forms of physical activity, except for anaerobic activities like weight lifting or sprinting, which are limited by low muscle glycogen levels.The article by Stephen D. Phinney explores the relationship between ketogenic diets and physical performance, challenging the common belief that a low-carbohydrate diet impairs physical performance. Drawing on historical observations from traditional Inuit culture, the author argues that with proper adaptation, optimized sodium and potassium nutrition, and controlled protein intake, individuals can maintain or even enhance endurance performance despite nutritional ketosis. Phinney reviews historical studies and personal experiences, including the Schwatka expedition and the work of Vilhjalmur Stefansson, who lived for a year on a diet consisting primarily of meat and fat. These accounts suggest that prolonged adaptation to a ketogenic diet can lead to improved physical stamina and endurance. The article also discusses modern studies conducted by Phinney and colleagues, which found that untrained and highly trained subjects experienced a delayed but full recovery in peak aerobic power and endurance performance after adapting to a ketogenic diet. The studies highlight the importance of adequate protein and mineral intake, particularly sodium and potassium, to maintain cardiovascular reserve and preserve lean body mass. Phinney concludes that while submaximal endurance performance can be sustained on a low-carbohydrate diet, careful attention to keto-adaptation time, mineral nutrition, and protein dosage is crucial. He emphasizes that therapeutic use of ketogenic diets should not restrict most forms of physical activity, except for anaerobic activities like weight lifting or sprinting, which are limited by low muscle glycogen levels.