Gawelczyk et al. 2026, Low-carbohydrate and ketogenic diets and aerobic performance: systematic review and meta-analysis

A systematic review and meta-analysis of 33 aerobic-focused studies (Nutrients 18(5):740; DOI: 10.3390/nu18050740) found that low-carbohydrate and ketogenic diets consistently raised fat oxidation (increases of 28–200 % across all 30 studies measuring it) but that performance effects were time-dependent: studies measuring outcomes within the first seven days showed declines, while those measuring after one week showed maintained or improved results. Exercise economy was impaired in 50 % of studies, and VO2max was stable or improved in the majority. The authors recommend periodised carbohydrate strategies that balance metabolic adaptation from low-carbohydrate training phases with carbohydrate availability for competition. Moderate evidence.