The whole‐body and skeletal muscle metabolic response to 14 days of highly controlled low energy availability in endurance‐trained females

This study investigated the effects of 14 days low energy availability (LEA) versus optimal energy availability (OEA) in endurance‐trained females on substrate utilization, insulin sensitivity, and skeletal muscle mitochondrial oxidative capacity; and the impact of metabolic changes on exercise performance. Twelve endurance‐trained females (V̇O2max 55.2 ± 5.1 mL × min−1 × kg−1) completed two 14‐day randomized, blinded, cross‐over, controlled dietary interventions: (1) OEA (51.9 ± 2.0 kcal × kg fat‐free mass (FFM)−1 × day−1) and (2) LEA (22.3 ± 1.5 kcal × kg FFM−1 × day−1), followed by 3 days OEA. Participants maintained their exercise training volume during both interventions (approx. 8 h × week−1 at 79% heart rate max). Skeletal muscle mitochondrial respiratory capacity, glycogen, and maximal activity of CS, HAD, and PFK were unaltered with LEA. 20‐min time trial endurance performance was impaired by 7.8% (Δ −16.8 W, 95% CI: −23.3 to −10.4, p