International society of sports nutrition position stand: ketogenic diets.

Alex Leaf, Jeffrey A Rothschild, Tim M Sharpe, Stacy T Sims, Chad J Macias, Geoff G Futch, Michael D Roberts, Jeffrey R Stout, Michael J Ormsbee, Alan A Aragon, Bill I Campbell, Shawn M Arent, Dominic P D'Agostino, Michelle T Barrack, Chad M Kerksick, Richard B Kreider, Douglas S Kalman, Jose Antonio

Journal: Journal of the International Society of Sports Nutrition 2024;21(1):2368167

PMID: 38934469

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Plain Language Summary

The use of ketogenic diets for enhancing sports performance and body composition has become increasingly popular. The International Society of Sports Nutrition (ISSN) has published several articles addressing nutrient requirements for optimising training adaptations and sports performance. This study’s aim was to provide an evidence-based assessment of the use of ketogenic diets in healthy exercising adults, focusing on exercise performance and body composition (the use of exogenous ketone supplements is not covered). This study is a review by the ISSN, offering evidence-based insights into ketogenic diets for athletes and fitness enthusiasts. This review indicates: A. Nutritional ketosis: - a ketogenic diet induces nutritional ketosis, defined as serum ketone levels above 0.5 mM. - daily carbohydrate intake should generally be less than 50 grams to achieve this state. B. Safety and distinction: - nutritional ketosis achieved through carb restriction and high dietary fat is not harmful. However, it should not be confused with ketoacidosis, a life-threatening condition seen in clinical populations. C. Athletic performance: - ketogenic diets have neutral or detrimental effects on athletic performance. Despite elevated fat oxidation during exercise, performance decrement occurs in elite athletes. D. Endurance effects: - endurance effects may vary based on training status and duration of dietary intervention. Limited evidence supports a benefit from ketogenic diets lasting more than six weeks. E. Strength and resistance training: - ketogenic diets have similar effects on maximal strength and strength gains. However, some studies show superior effects with non-ketogenic diets. F. Body composition: - ketogenic diets may cause greater weight, fat mass, and fat-free mass losses (differences in calories, protein intake, and fluid balance contribute to these results). G. Sex differences: - there is insufficient evidence on sex-specific effects of ketogenic diets. Authors concluded that ketogenic diets can be considered for specific purposes in exercising adults, but further research is needed to fully understand their effects.

Abstract

POSITION STATEMENT

The International Society of Sports Nutrition (ISSN) provides an objective and critical review of the use of a ketogenic diet in healthy exercising adults, with a focus on exercise performance and body composition. However, this review does not address the use of exogenous ketone supplements. The following points summarize the position of the ISSN.

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1. A ketogenic diet induces a state of nutritional ketosis, which is generally defined as serum ketone levels above 0.5 mM. While many factors can impact what amount of daily carbohydrate intake will result in these levels, a broad guideline is a daily dietary carbohydrate intake of less than 50 grams per day.

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2. Nutritional ketosis achieved through carbohydrate restriction and a high dietary fat intake is not intrinsically harmful and should not be confused with ketoacidosis, a life-threatening condition most commonly seen in clinical populations and metabolic dysregulation.

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3. A ketogenic diet has largely neutral or detrimental effects on athletic performance compared to a diet higher in carbohydrates and lower in fat, despite achieving significantly elevated levels of fat oxidation during exercise (~1.5 g/min).

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4. The endurance effects of a ketogenic diet may be influenced by both training status and duration of the dietary intervention, but further research is necessary to elucidate these possibilities. All studies involving elite athletes showed a performance decrement from a ketogenic diet, all lasting six weeks or less. Of the two studies lasting more than six weeks, only one reported a statistically significant benefit of a ketogenic diet.

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5. A ketogenic diet tends to have similar effects on maximal strength or strength gains from a resistance training program compared to a diet higher in carbohydrates. However, a minority of studies show superior effects of non-ketogenic comparators.

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6. When compared to a diet higher in carbohydrates and lower in fat, a ketogenic diet may cause greater losses in body weight, fat mass, and fat-free mass, but may also heighten losses of lean tissue. However, this is likely due to differences in calorie and protein intake, as well as shifts in fluid balance.

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7. There is insufficient evidence to determine if a ketogenic diet affects males and females differently. However, there is a strong mechanistic basis for sex differences to exist in response to a ketogenic diet.

Address: Alex Leaf LLC, Scientific Affairs, Scottsdale, AZ, USA.; Auckland University of Technology, Sports Performance Research Institute New Zealand, Auckland, New Zealand.; High Performance Sport New Zealand, Performance Nutrition, Auckland, New Zealand.; University of Western States, Human Nutrition and Functional Medicine, Portland, OR, USA.; Auckland University of Technology, Sports Performance Research Institute New Zealand, Auckland, New Zealand.; Stanford University, Stanford Lifestyle Medicine, Palo Alto, CA, USA.; Springfield College, Department of Exercise Science and Athletic Training, Springfield, MA, USA.; FitPro Analytics, Scientific Affairs, Springfield, MA, USA.; Auburn University, School of Kinesiology, Auburn, AL, USA.; University of Central Florida, School of Kinesiology and Rehabilitation Sciences, Orlando, FL, USA.; Florida State University, Institute of Sports Sciences & Medicine, Tallahassee, FL, USA.; University of KwaZulu Natal, Discipline of Biokinetics, Exercise and Leisure Sciences, Durban, South Africa.; Fit Advancement, LLC. Chatsworth, CA, USA.; University of South Florida, Performance and Physique Enhancement Laboratory, Exercise Science Program, Tampa, FL, USA.; University of South Carolina, Department of Exercise Science, Arnold School of Public Health, Columbia, SC, USA.; Institute for Human and Machine Cognition, Human Healthspan, Resilience, and Performance, Pensacola, FL, USA.; University of South Florida, Department of Molecular Pharmacology and Physiology, Tampa, FL, USA.; California State University, Department of Family and Consumer Sciences, Long Beach, CA, USA.; Lindenwood University, Exercise and Performance Nutrition Laboratory, College of Science, Technology, and Health, St. Charles, MO, USA.; Texas A&M University, Exercise and Sport Nutrition Lab, Department of Kinesiology and Sports Management, College Station, TX, USA.; Nova Southeastern University, Department of Nutrition. Dr. Kiran C. Patel College of Osteopathic Medicine. Davie, FL, USA.; Department of Health and Human Performance, Nova Southeastern University, Davie, FL, USA.

DOI: 10.1080/15502783.2024.2368167