Abstract
ative review aims to highlight the effect of the Ketogenic diet on aerobic and anaerobic athletic performance. This paper adopts a narrative approach exposing the results of approximately 40 earlier studies to define the scope of applying the ketogenic diet as a nutritional therapy, aiming to aid recovery from fatigue or muscle damage caused by exercise and to increase aerobic and anaero- bic performance. A ketogenic diet appears better suited for lower-intensity physical activities conducted in a balanced or moderate state of energy demand. However, there is a lack of consensus on its compatibility with strength exercises that require maximal bursts of ener- gy. These investigations should explore its effects on performance, health, and body composition compared to other dietary approaches. Ultimately, a better understanding of the ketogenic diet's benefits and limitations will help athletes and individuals make informed deci- sions about its adoption for optimizing their health and athletic goals. Keywords: Injuries, ketogenic, ketosis, aerobic exercises, anaerobic exercises, muscle damage Resumen. Esta revisión narrativa tiene como objetivo resaltar el efecto de la dieta cetogénica sobre el rendimiento deportivo aeróbico y anaeróbico. Este artículo adopta un enfoque narrativo exponiendo los resultados de aproximadamente 40 estudios anteriores para definir el alcance de la aplicación de la dieta cetogénica como terapia nutricional, con el objetivo de ayudar a la recuperación de la fatiga o daño muscular causado por el ejercicio y aumentar el rendimiento aeróbico y anaeróbico. Una dieta cetogénica parece más adecuada para actividades físicas de menor intensidad realizadas en un estado de demanda energética equilibrado o moderado. Sin embargo, existe una falta de
de la dieta cetogénica como terapia nutricional, con el objetivo de ayudar a la recuperación de la fatiga o daño muscular causado por el ejercicio y aumentar el rendimiento aeróbico y anaeróbico. Una dieta cetogénica parece más adecuada para actividades físicas de menor intensidad realizadas en un estado de demanda energética equilibrado o moderado. Sin embargo, existe una falta de consenso sobre su compatibilidad con ejercicios de fuerza que requieren explosiones máximas de energía. Estas investigaciones deberían explorar sus efectos sobre el rendimiento, la salud y la composición corporal en comparación con otros enfoques dietéticos. En última instancia, una mejor comprensión de los beneficios y limitaciones de la dieta cetogénica ayudará a los atletas y a las personas a tomar decisiones informadas sobre su adopción para optimizar su salud y sus objetivos deportivos. Palabras clave: Lesiones, cetogénicas, cetosis, ejercicios aeróbicos, ejercicios anaeróbicos, daño muscular. Fecha recepción: 24-04-24. Fecha de aceptación: 13-09-24 Abdullah Alzahrani aalzahrani@su.edu.sa Introduction The Ketogenic diet, also known as the ketosis diet, is a "low-carbohydrate" and "high-fat" diet that has gained popu- larity in recent years. Ketogenic diet has been explored across various health domains including weight management, diabetes control, cardiovascular health, neurological diseas- es, cancer treatment, and athletic performance. This diet involves reducing carbohydrate intake and increasing fat intake to induce a state of ketosis in the body. The ketosis— a metabolic state where fat is utilized as a primary energy source instead of carbohydrates—leading to significant re- ductions in body weight and improvements in glycemic control (O’neill & Raggi, 2019). However, concerns have been raised regarding the long-term sustainability of such diets due to potential adverse effects on lipid profiles (Brouns, 2018). Ketogenic diet exhibits strong anti- inflammatory properties that may confer cardioprotective benefits through mechanisms such as reducing inflammation markers and providing an alternative energy source for heart cells during stress conditions (Dyńka et al., 2023). Research indicates that the ketogenic diet may facilitate an increase in fat oxidation during exercise, potentially providing a meta- bolic advantage for endurance athletes. For instance, studies have shown that adherence to a ketogenic low-carbohydrate high-fat diet can enhance
such as reducing inflammation markers and providing an alternative energy source for heart cells during stress conditions (Dyńka et al., 2023). Research indicates that the ketogenic diet may facilitate an increase in fat oxidation during exercise, potentially providing a meta- bolic advantage for endurance athletes. For instance, studies have shown that adherence to a ketogenic low-carbohydrate high-fat diet can enhance the muscle's ability to utilize fat as a fuel source, thereby sparing glycogen stores for prolonged endurance activities (Cao et al., 2021). However, these benefits may come at the cost of performance during high- intensity efforts. Evidence suggests that while fat oxidation rates can double within a few weeks of adopting a ketogenic low-carbohydrate high-fat diet, the ability to utilize glycogen effectively may diminish, leading to compromised perfor- mance in high-intensity scenarios (Wang et al., 2022). Meta- analyses focusing on endurance athletes have yielded mixed results regarding the efficacy of the ketogenic diet on per- formance metrics such as VO2max and time to exhaustion. A systematic review and meta-analysis encompassing ten studies found no significant improvements in aerobic capaci- ty or exercise performance attributable to ketogenic low- carbohydrate high-fat diets (Cao et al., 2021). Similarly, another review assessing concurrent training combined with ketogenic low-carbohydrate high-fat diets also reported no significant effects on body composition or aerobic perfor- mance compared to other dietary strategies (Podlogar & Wallis, 2022). Several systematic reviews have been conducted to assess the impact of ketogenic diet on strength and endurance performance. For instance, one systematic review found that while ketogenic diet may enhance fat oxidation during exer-
2024, Retos, 60, 1237-1243 © Copyright: Federación Española de Asociaciones de Docentes de Educación Física (FEADEF) ISSN: Edición impresa: 1579-1726. Edición Web: 1988-2041 (https://recyt.fecyt.es/index.php/retos/index) -1238- Retos, número 60, 2024 (noviembre) cise, its effects on overall physical performance remain con- tentious. In endurance activities, results have been mixed; some studies report no significant differences in performance between those on a ketogenic diet and those consuming a mixed macronutrient diet (Murphy et al., 2021). In con- trast, other studies suggest that prolonged adherence to a ketogenic diet could lead to impairments in high-intensity exercise performance due to reduced muscle glycogen avail- ability (Ashtary-Larky et al., 2022). When examining anaerobic performance, particularly in resistance training contexts, the evidence suggests that keto- genic diet does not significantly hinder strength gains in trained individuals. A systematic review highlighted that while there were no notable differences in one-repetition maximum (1-RM) strength tests between ketogenic and control groups, there was a tendency for slight improve- ments in favor of the ketogenic group (Koerich et al., 2022). However, concerns about potential reductions in fat-free mass when following a ketogenic diet persist, especially among resistance-trained athletes (Vargas-Molina et al., 2022). Paoli, (2014) described ketosis as a natural metabolic state where, instead of carbohydrates, ingested glucose acts as the key energy resource for the body. Here, the body reallocates fat as the primary energy source and breaks it down into ketone bodies, enabling it to be utilized as the main energy by most tissues, including muscles and the brain (McSwiney et al., 2019). The impacts of ketogenic diet across different health contexts necessitating personalized approaches considering athletes characteristics alongside existing clinical guidelines ensuring balanced considerations around potential risks versus benefits tailored accordingly. Ketogenic diet has been proposed as a strategy to enhance sports performance by augmenting fat oxidation during prolonged exercise. This metabolic adaptation is hypothe- sized to preserve glycogen stores, potentially extending endurance performance capacity (Burke, 2021; Burke et al., 2021). However, the effect of ketogenic diet on sports per- formance remains contentious due to mixed findings across various athletic disciplines. Thus, this narrative review aims to describe the
to enhance sports performance by augmenting fat oxidation during prolonged exercise. This metabolic adaptation is hypothe- sized to preserve glycogen stores, potentially extending endurance performance capacity (Burke, 2021; Burke et al., 2021). However, the effect of ketogenic diet on sports per- formance remains contentious due to mixed findings across various athletic disciplines. Thus, this narrative review aims to describe the effects of the ketosis diet on aerobic and anaerobic athletic performance. Material and Methods A literature search was achieved using PubMed, Medline, and Google Scholar databases to achieve this purpose. The search items consisted of related terms such as 'ketogenic', 'ketosis diet', 'performance', 'keto', 'ketone bodies', 'low- carbohydrate', 'low-fat', 'high-carbohydrate', 'high-fat', 'aer- obic exercises', 'anaerobic exercises', 'fatty acids', 'body- composition', 'endurance athlete', 'weight loss', 'lactic acid', etc. Manual searches of undigitized journals, papers, and articles were also undertaken, focusing on meta-analysis re- evaluations of the ketosis diet and its role in performance optimization. We included only studies which is directly related to aerobic or anaerobic sports performance. Any study related to any other issue except sports performance was excluded form this review. Interpretation Recapitulation of the ketogenic diet Research has proved that the ketogenic diet works on var- ious mechanisms simultaneously to generate certain maximal benefits compared to other dietary regimes. The basic function of the ketosis diet is to curb carbohy- drates to produce improved insulin sensitivity (reduce insu- lin resistance) while lowering the risk for some chronic diseases, such as cancer, cardiovascular diseases, and diabe- tes. However, in the absence of the carbohydrates needed to provide the body's energy requirements, fat becomes the substitute fuel. This change is of more assistance in produc- ing comparatively early weight loss than the loss of body mass caused by other dietary regimes. The ketogenic diet relies on using accumulated body fat and any fat derived from the food intake. The liver is active in breaking down fat to produce the three ketone bodies, one of which is BHB. Conversely, the energy molecules derived from ketone bodies provide a 'pure' source of high energy for the brain, which reduces inflammation in the
regimes. The ketogenic diet relies on using accumulated body fat and any fat derived from the food intake. The liver is active in breaking down fat to produce the three ketone bodies, one of which is BHB. Conversely, the energy molecules derived from ketone bodies provide a 'pure' source of high energy for the brain, which reduces inflammation in the central nervous system and improves mental clarity. However, as in many other cases of dietary restriction, the ketogenic diet also has some side effects in the prelimi- nary stages, such as fatigue, headache, dizziness, sleep dis- turbances, cramps, heart palpitations, and diarrhoea or con- stipation [1-29]. Furthermore, it is considered by some authorities in the field that reliance on a diet loaded with animal fats and proteins can lead to the risk of developing cardiovascular disease, with elevated cholesterol levels and high blood pressure (hypertension). In this context, Paoli et al. (2012) reported that most ketogenic diets have low mag- nesium, vitamin D, calcium, and folic acid levels. If the diet is not carefully planned, this could lead to nutrient insuffi- ciencies. Thus, nutritionists and clinicians advocate detailed planning for optimum benefits from the ketogenic diet. Gateway to enhanced sports performance The purpose of the ketogenic diet has changed in the last twenty years, and it is no longer only a therapeutic proce- dure for treating patients. It is gaining popularity as a weight-loss regime but has also received some recognition as a performance-optimization tool for athletes. Many re- searchers have tried recently to confirm the positive aspects of the ketogenic diet for optimizing sports performance by boosting athletes' strength and endurance. Several studies have reported substantial increases in fat oxidation rates
2024, Retos, 60, 1237-1243 © Copyright: Federación Española de Asociaciones de Docentes de Educación Física (FEADEF) ISSN: Edición impresa: 1579-1726. Edición Web: 1988-2041 (https://recyt.fecyt.es/index.php/retos/index) -1239- Retos, número 60, 2024 (noviembre) among elite athletes following a ketogenic diet regimen. Burke et al. highlighted that even within elite endurance athletes, adherence to a ketogenic diet could double exercise fat use to approximately 1.5 g min^-1 (Burke, 2021). De- spite these metabolic shifts favoring increased lipid utiliza- tion during submaximal exercise intensities (~70% maximal aerobic capacity), concerns arise regarding the diet's impact on higher-intensity efforts (>80% maximal aerobic capaci- ty). Herein lies a critical limitation: keto-adaptation may impair muscle glycogen utilization during high-intensity bouts where carbohydrates are more efficiently metabolized than fats (Burke et al., 2021). Some athletes may experience enhanced endurance capabilities post-adaptation, others report deteriorated performance outcomes (Burke et al., 2021). Burke et al.'s (2017) study involving elite race walk- ers found that while both dietary approaches improved peak aerobic capacity (V̇O2 peak), only those adhering to high- carbohydrate protocols demonstrated improvements in race times—a stark contrast against their LCHF counterparts who showed no such benefit despite heightened fat oxidation capacities. Moreover, short-term adaptations to ketogenic diet can rapidly enhance fat oxidation but fail to improve or even impair endurance exercise metabolism and perfor- mance despite increased glycogen availability (Devrim- Lanpir et al., 2021). The Ketogenic diet has been shown to have numerous health benefits, including weight loss, im- proved blood sugar control, and reduced risk of heart dis- ease. However, this diet has also gained attention in the athletic community as a way to optimize both aerobic and anaerobic performance. Research has shown that the Keto- genic diet can improve aerobic and anaerobic athletic per- formance. Ketogenic and anaerobic exercise Sports activities requiring intense energy expenditure for short bursts are considered anaerobic exercises. The physio- logical process in these exercises involves breaking down glucose for energy without using oxygen. These activities release energy within a small period but with high intensity when oxygen demand surpasses oxygen supply. The rela- tionship between ketogenic diets and anaerobic exercise performance presents a complex
Sports activities requiring intense energy expenditure for short bursts are considered anaerobic exercises. The physio- logical process in these exercises involves breaking down glucose for energy without using oxygen. These activities release energy within a small period but with high intensity when oxygen demand surpasses oxygen supply. The rela- tionship between ketogenic diets and anaerobic exercise performance presents a complex interplay influenced by adaptations in fuel utilization, body composition changes, and potential impacts on high-intensity exercise capabilities. The critical examination of recent literature reveals nuanced findings that challenge traditional paradigms surrounding carbohydrate dependency for peak athletic performance. Several studies demonstrate that adaptation to Low Crab and High Fat (LCHF) diets results in significantly enhanced fat oxidation rates during exercise (Noakes et al., 2023), with one study documenting peak fat oxidation rates over 1.5 g/min at intensities exceeding 85% VO2max (Noakes et al., 2023). This shift potentially allows for sustained energy production from fat stores even during higher intensity ef- forts traditionally believed to rely predominantly on carbo- hydrate metabolism. However, it's essential to acknowledge the variability in individual responses to such dietary inter- ventions, as highlighted by Prins et al., who noted record- high peak fat oxidation rates alongside maintained high- intensity performance at ∼85%VO2max following LCHF diet adaptation (Prins et al., 2023). Contrasting these posi- tive outcomes are findings suggesting impairments in anaer- obic performance metrics post-adaptation to ketogenic diets. Wroble et al.'s (2019) randomized-sequence crossover trial reported significant reductions in both peak power output and mean power during Wingate tests following a short- term low-carbohydrate ketogenic diet intervention com- pared to a high-carbohydrate diet among trained individuals. These results underscore potential limitations of ketogenic diets concerning immediate energy requirements character- istic of anaerobic activities. Moreover, Burke et al.'s investi- gation into elite race walkers revealed an increased oxygen cost associated with speeds pertinent to competitive events after brief keto-adaptation periods despite enhanced glyco- gen availability (Burke et al., 2017). Such observations sug- gest that while LCHF diets may improve substrate availabil- ity through elevated fat oxidation rates and glycogen conser- vation/storage mechanisms, they might concurrently impair exercise economy—potentially
investi- gation into elite race walkers revealed an increased oxygen cost associated with speeds pertinent to competitive events after brief keto-adaptation periods despite enhanced glyco- gen availability (Burke et al., 2017). Such observations sug- gest that while LCHF diets may improve substrate availabil- ity through elevated fat oxidation rates and glycogen conser- vation/storage mechanisms, they might concurrently impair exercise economy—potentially negating benefits derived from altered fueling strategies during actual competition scenarios (Tiller et al., 2019). Additionally, McSwiney et al.'s (2019) longitudinal study involving endurance athletes indicated no decrement in moderate-to-vigorous intensity exercise performance following keto-adaptation; however, decreases in exercise economy were observed above 70% VO2max. This aligns with concerns regarding the efficiency of energy utilization under ketosis at higher intensities where rapid ATP turnover is crucial. It's also noteworthy that sev- eral investigations have pointed out improvements or neutral effects on specific aspects of physical performance (e.g., sprint times) alongside favorable body composition altera- tions subsequent to transitioning towards lower carbohy- drate intakes (Prins et al., 2019; Volek et al., 2016). Yet questions remain about long-term sustainability and broader applicability across different athletic populations given in- herent study limitations including small sample sizes and short-duration interventions. In synthesizing available evi- dence within this contextually rich landscape fraught with contradictory findings and methodological disparities among studies (ranging from acute dietary manipulations spanning days weeks months), it becomes evident there exists no one- size-fits-all nutritional strategy suitable across all modalities intensity domains within sport-specific settings particularly when considering anaerobic versus aerobic demands distinct physiological bases underlying each mode exertion. In this context, several studies have assessed the impact
2024, Retos, 60, 1237-1243 © Copyright: Federación Española de Asociaciones de Docentes de Educación Física (FEADEF) ISSN: Edición impresa: 1579-1726. Edición Web: 1988-2041 (https://recyt.fecyt.es/index.php/retos/index) -1240- Retos, número 60, 2024 (noviembre) of the Ketogenic diet on athletes' performance during anaer- obic exercise in various populations. While considering various factors among endurance game players (McSwiney et al., 2018), Cross-Fit contestants (Gregory, 2017), gymnas- tic players (Paoli, Grimaldi, D’Agostino, et al., 2012), and power-lifters (Greene et al., 2018). Recently, a significantly increased relative power, instead of absolute or total power, has been revealed, resulting from reduced body weight among subjects (McSwiney et al., 2018) in athletes perform- ing endurance exercises. Other studies demonstrated a re- duced thickness of skeletal muscle or lean body mass (Kephart et al., 2018). A study published in the International Journal of Sports and Exercise Medicine found that athletes on a Ketogenic diet had significantly higher peak power output during high-intensity exercise than those on a high- carbohydrate diet (Gregory, 2017). The integration of current research suggests that while ketogenic or LCHF diets can enhance fat oxidation capacity possibly offering metabolic advantages under certain condi- tions their application as universal ergogenic aids especially concerning anaerobic sports disciplines remains questionable due complexities surrounding individual variability metabol- ic flexibility impact on exercise economy overall implica- tions for high-intensity performances requiring immediate explosive energy outputs Hence further rigorous long-term investigations are warranted better elucidate optimal dietary frameworks conducive maximizing athlete health functional capacities across diverse sporting endeavors. Ketogenic diet and aerobic exercise Aerobic exercise, popularly known as 'cardio', provides cardiovascular conditioning. The amount of oxygen available to the muscles for burning fuel and movement is controlled by breathing. Aerobic activity, including swimming and running, strengthens the respiratory system and increases lung capacity while maintaining a healthy heart. Unlike an- aerobic exercises, performed using the greatest effort over a lesser time, aerobic exercises are performed at a lower in- tensity for a comparatively longer period. The intensity and duration of aerobic exercise (Egan & Zierath, 2013) deter- mine the role of fatty acids in the oxidation process. In activ- ities requiring only a
while maintaining a healthy heart. Unlike an- aerobic exercises, performed using the greatest effort over a lesser time, aerobic exercises are performed at a lower in- tensity for a comparatively longer period. The intensity and duration of aerobic exercise (Egan & Zierath, 2013) deter- mine the role of fatty acids in the oxidation process. In activ- ities requiring only a moderate amount of strength, exogenic fatty acids' oxidation provides a great energy source. How- ever, including fatty acid production increases activity dura- tion during low-intensity activities. Continuous availability of fatty acids is required for optimal performance during endurance exercise. For aerobic endurance activity, the ketogenic diet may be more beneficial than other diets since it encourages using fat as an energy source rather than carbohydrates. While adi- pose tissue fat provides an endless energy supply, internal carbohydrate storage via glucose in the liver and tissues is limited. The raised ketones from the Ketogenic diet may offer an alternative fuel source for sustaining exercise per- formance. Cao et al., (2021) found no significant effect of KD on aerobic capacity or exercise performance among endurance athletes through their systematic review and meta-analysis. This is echoed by Burke et al.'study (2017), where adaptation to an LCHF diet impaired performance in elite endurance athletes despite improvements in peak aero- bic capacity—a result attributed to reduced exercise econ- omy under a ketogenic state. Many studies in the past two decades observed the consequence of a low carbohydrate diet on the athlete's performance. The studies focused pri- marily on endurance-trained male athletes. The caloric in- take from fat ranged up to 80%, with protein between 15 and 29%, and that from carbohydrates being the least, at 3.5 to 15%. Periods under study they were varied from a level of three weeks to twenty months (Burke et al., 2017; Greene et al., 2018). As a result, serum ketone body beta- hydroxybutyrate concentrations increased from 0.5 to 1.2 mmol/L. Most of the research highlighted considerable decline in body weight (Burke et al., 2021; Cao et al., 2021; Egan & Zierath, 2013; Gregory, 2017; McSwiney et al., 2019; Wroble
a level of three weeks to twenty months (Burke et al., 2017; Greene et al., 2018). As a result, serum ketone body beta- hydroxybutyrate concentrations increased from 0.5 to 1.2 mmol/L. Most of the research highlighted considerable decline in body weight (Burke et al., 2021; Cao et al., 2021; Egan & Zierath, 2013; Gregory, 2017; McSwiney et al., 2019; Wroble et al., 2019). The results supported the use of the KETOGENIC DIET as an efficient dietary plan for re- ducing weight and balancing a sports person's physique. Although positive changes had been shown in body and fat mass in these studies, the low carbohydrate Ketogenic diet had failed effectively and significantly to improve the per- formance of athletes, even with a considerable decrease in respiratory exchange ratio (RER) and an increase in fatty acid oxidation. However, after examining five separate stud- ies, it was concluded that the metabolic state of ketogenic had improved physical endurance among 39 high-performance athletes due to the ability of the body to utilize fat as a substitute source of energy for oxidative respi- ration (Cox et al., 2016). Muscle catabolism and plasma- lactate concentration decreased through ketogenic, provid- ing an alternate substrate oxidation procedure. Ketogenic enhances intra-muscular triacylglycerol lipase function while exercising, in the occurrence of carbohydrates, muscle gly- cogen, and a raised glucose level. Another study of 20 en- durance athletes had similarly noticed improved perfor- mance, with fat loss, compared to a high carbohydrate con- trast group, after 12 weeks on the Ketogenic diet (McSwiney et al., 2018). Researchers found that athletes on a Ketogenic diet had significantly higher VO2 max levels than those on a high-carbohydrate diet. VO2 max measures an athlete's maximal oxygen uptake and indicates aerobic fitness (McSwiney et al., 2018). Nevertheless, clinical as- sessment and observational experiences from time to time have shown divergent results regarding the performance- optimization abilities of the Ketogenic diet. One review observed that increased levels of ketone bodies due to sup- plements may speed up muscle recovery and reduce protein
Description
The review discusses the ketogenic diet's impact on athletic performance based on previous studies.