Effects of ketogenic diet on performance and body composition in athletes and trained adults: systematic review and meta-analysis of randomized clinical trials

Abstract

Background: Low-carbohydrate, high fat ketogenic diet (KD) have been used as nutritional approach for clinical use. However, the KD has gained popularity for athletes and trained people to influence exercise performance, body composition and promote keto-adaptation. Objective: A systematic review and meta-analysis was conducted to determine the effects of KD on performance and body composition in athletes and trained people. Methods: Data Sources: MEDLINE, EMBASE, CINAHL, SPORTDiscus and The Cochrane Library were searched, along with the reference lists of included articles. Study Selection: Randomized clinical trial (RCT) in athletes or trained adults following an intervention protocol with KD, assessing any of the outcomes of interest. Data Extraction: Data were extracted independently by two researchers. Results: Eight studies identified up to June 27, 2019 were included in meta-analysis. Regarding outcomes, 8 studies assessed performance (5 studies for endurance and 3 for resistance) and 4 studies assessed body composition (3 studies of resistance and 1 study of endurance exercise). Meta-analysis showed no significant change for endurance (Δ = -3.20%; 95% CI -7.90 to 1.40%; p = 0.2780) and also for strenght performance (Δ = -0.50%; 95% CI -2.70 to 1.80%; p = 0.6787) with KD intervention. About body composition for resistance athletes, meta-analysis showed significant change favorable to KD for body weight (Δ = -2.00%; 95% CI, -3.30 to -0.70%; p = 0.0031), significant change favorable to control diet for fat free mass (Δ = 1.40%; 95% CI, 0.30 to 2.50%; p = 0.0154) and no significant alteration for body fat (Δ = -0.70%; 95% CI, -1.60 to 0.20%; p = 0.1197). No meta-analysis was assessed for body composition in endurance athletes because there is no data analysis available. Conclusions: KD showed no conclusive results for performance in endurance or resistance exercise in athletes or trained adults. For body composition, the findings indicate weight and fat free mass loss with KD, without conclusive results for body fat.