<p>Impact Of Ketogenic Diet On Athletes: Current Insights</p>

Abstract

The impact of a ketogenic diet (KD) (<50 g/d carbohydrate, >75% fat) on athletic performance has sparked much interest and self-experimentation in the past 3–4 years. Evidence shows 3–4-week adaptations to a KD in endurance-trained athletes were associated with maintenance of moderate (46–63% VO2max) and vigorous intensity (64–90% VO2max) endurance exercise, while at intensities >70% VO2max, increases in fat oxidation were associated with decreased economy (increased oxygen consumption), and in some cases, increased ratings of perceived exertion and heart rate. Two investigations in recreationally active endurance athletes noted no vigorous intensity exercise decrement following 3- and 12-week adaptations. Moderate (70–85% one repetition maximum) and near-maximal to maximal intensity (>85% 1RM) strength performance experienced no decrement following a 3-12-week KD adaptation. Beneficial effects were noted for 2000 m sprint and critical power test completed for short duration at vigorous intensity, while two additional tests noted no decrement. For sprint, near-maximal exercise (>91% VO2max), benefit of the KD was observed for six-second sprint, while no decrement in performance was noted for two additional maximal tests. When protein is equated (grams per kilogram), one investigation noted no decrement in muscle hypertrophy, while one noted a decrement. One investigation with matched protein noted the KD group lost more body fat. In conclusion, moderate-to-vigorous intensity exercise experiences no decrement following adaptation to a KD. Decreases in exercise economy are observed >70% VO2max in trained endurance athletes which may negate performance within field settings. Beneficial effects of the KD during short duration vigorous, and sprint bouts of exercises are often confounded by greater weight loss in the KD group. With more athletes pursuing carbohydrate-restricted diets (moderate and strict (KD)) for their proposed health benefits, more work is needed in the area to address both performance and health outcomes.

A review of the ketogenic diet for endurance athletes: performance enhancer or placebo effect?

“…Several biological mechanisms may help to explain the potential for mixed and/or detrimental effects, including changes in fuel economy, production of certain metabolic byproducts, and reduced energy intake. For example, the EAKD significantly increases fat oxidation, requiring greater oxygen consumption due to the increased oxygen demands during fatty acid metabolism versus carbohydrate metabolism [12,22]. This increased demand for oxygen reduces the beneficial impact of an increased VO 2 max because a greater percentage of maximal oxygen uptake is now required to maintain any given race pace [13].…”

Effects of a ketogenic diet on body composition and strength in trained women

“…In the context of physical performance, it can be speculated that KDs do not produce better results than carbohydrate-rich diets, although they could have limited benefits or, at least, not harmful to performance under certain scenarios [13]. Thus, a KD conceivably may be a plausible nutritional strategy in specific scenarios, such as: i) during prolonged low-intensity events predominantly reliant on fat oxidation to fuel exercise; ii) during the pre-competition carbohydrate-restriction phase prior to bodybuilding and/or physique competitions when it is advantageous to restrict carbohydrate intake; and/or iii) for individuals who prefer to lowcarbohydrate diets [14].…”

The Influence of Cyclical Ketogenic Reduction Diet vs. Nutritionally Balanced Reduction Diet on Body Composition, Strength, and Endurance Performance in Healthy Young Males: A Randomized Controlled Trial

“…The influence of ketogenic diets on sports performance is still the topic of an ongoing debate [ 10 , 11 ] with often conflicting results [ 12 ]. The overreaching mainstream nutrition philosophy for endurance athletes emphasizes a carbohydrate-dominant, low fat paradigm.…”