International society of sports nutrition position stand: ketogenic diets.
Level 5 - mechanism / opinion, no new human data
Professional society position stand and narrative review
PubMed 38934469 · doi:10.1080/15502783.2024.2368167
What was done
The International Society of Sports Nutrition (ISSN) synthesized available literature to produce a formal position stand evaluating the effects of a ketogenic diet (broadly defined as carbohydrate intake <50 g/day inducing serum ketones >0.5 mM) on exercise performance and body composition in healthy exercising adults. Exogenous ketone supplementation was excluded.
What was found
Ketogenic diets markedly elevated exercise fat oxidation (~1.5 g/min) but produced mostly neutral or detrimental effects on athletic performance relative to higher-carbohydrate diets. In elite athletes, all identified studies (all lasting ≤6 weeks) demonstrated performance decrements; of two studies lasting >6 weeks across all populations, only one found a statistically significant benefit. Maximal strength and resistance training adaptations were generally similar between ketogenic and higher-carbohydrate diets, with a minority favoring non-ketogenic controls. Ketogenic diets produced greater reductions in body weight, fat mass, and fat-free/lean mass, likely mediated by calorie, protein, and fluid shifts. Data regarding sex differences remain insufficient.
Why it matters
This position stand clarifies that elevated fat oxidation under nutritional ketosis does not translate into superior athletic performance and can impair high-level endurance capacity, helping athletes and practitioners make evidence-informed dietary choices.
Limits
The abstract describes a position consensus rather than a formal systematic review or meta-analysis, and total study and participant counts are not reported. Most trials in elite athletes were short-term (≤6 weeks), and alterations in lean mass are heavily confounded by fluid shifts and variable protein/caloric intakes. Data in female athletes are sparse.
Cited by
- partial Athletes following a ketogenic diet did not experience deterioration in physical performance compared to those on a high-carbohydrate diet.