Our metabolic system is remarkably flexible in its ability to use a variety of food macronutrients as fuel. Traditionally, carbohydrate diets have been recommended for sport (1,2,3,4,5). Carbohydrate loading is one of the main nutritional strategies to improve physical performance before crucial events (6,7,8,9,10). However, for excellent athletes practicing endurance sports, this strategy can lead to a delicate dilemma. The ability of the human body to store carbohydrates is limited, which corresponds to 5 grams of glucose in the bloodstream and about 100 grams or about 500 grams of glycogen in skeletal muscle or liver. A person of average weight can store 10 kg of fat in the body, which makes it able to finish> 30 marathon races if the stored fat is used effectively (11,12,13,14). However, the abundant carbohydrates in traditional high fat diets can prevent us from using fats (15,16,17,18,19,20). It is therefore important to know if we can find an effective way to improve the use of fat.
A ketogenic diet (KD) consists of using fat, a high density substrate, as the main source of daily caloric intake while limiting carbohydrate intake (21,22). In this way, the liver is obliged to produce and release ketone bodies in the circulation (23,24,25,26). This phenomenon is called nutritional ketosis (27,28,29). Over time, the body will become accustomed to the use of ketone bodies as the main fuel, called keto-adaptation, an element of adaptation to fat (30, 31, 32). Glucose oxidation requires 11 steps to produce energy, while fat and ketone bodies can quickly provide energy in just three steps (33,34). In any case, the body's ability to reserve ketones and fat is much stronger. Compared to glucose, ketone bodies consume more energy, while a metabolism centered on the ketone body is likely to provide a constant and rapid energy supply (35). Despite the potential for increased performance and physical capacity, a KD can also contribute to muscle health through anti-inflammatory and antioxidant properties, preventing fatigue and exercise-induced muscle and systemic injury. (35,36,37,38,39, 40,41,42,43,44). Compared with glucose oxidation, fat – centered oxidation involves the production of less reactive oxygen species during the process. Excessive free radicals and chronic inflammation are harmful to mitochondria, muscle cells and whole body health (45). The long-term administration of KD is related to the reduction of mediators of inflammation by downregulating the expression of the inflammasome of protein 3 containing the NACHT, LRR domain. and PYD (NLRP3) and reducing the generation of isoprostanes (46,47). It has also been reported that a high-fat diet could contribute to mitochondrial biogenesis and reduce mitochondrial autophagy, thus contributing to the constitution of a rich mitochondrial reservoir in the muscle, improving physical performance. and contributing to the well-being of athletes (48,49).
Given the strong foundation of its potential to improve exercise capacity, many KD and exercise investigations have been conducted in recent years. The purpose of this review is to summarize in a narrative way the recent literature (mainly articles published over the last three years) on the potential of KD as a nutritional approach to endurance exercise. We conducted a thorough search in MedLine with the keywords diet, ketogenic, ketone, ketosis and other keywords to access related articles. This article focuses primarily on endurance capacity, fatigue recovery and the multi-faceted approach to preventing muscle and organ damage caused by exercise.
Sports | Free Full Text | Keto-adaptability and endurance capacity, recovery of fatigue and prevention of exercise-induced muscle and organ damage: narrative review
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