Gejl & Nybo 2021, periodized carbohydrate restriction meta-analysis

A systematic review and meta-analysis of nine controlled training studies in well-trained endurance athletes found no statistically significant performance benefit of periodised carbohydrate restriction (train-low) compared with conventional high-carbohydrate training (SMD = 0.17 [−0.15, 0.49]; P = 0.29). Although acute mechanistic work reliably shows amplified molecular signalling under low-glycogen conditions, the pooled evidence does not support a performance-enhancing effect. Moderate evidence.