Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: A systematic review and meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of intervention studies
PubMed 29315892 · doi:10.1111/sms.13054
What was done
This systematic review and meta-analysis investigated the effects of exercising in a fasted versus fed state on aerobic, anaerobic, or intermittent performance and post-exercise metabolic responses. Literature searches were conducted via MEDLINE and PubMed, identifying 46 studies meeting inclusion criteria. Study quality was evaluated using the Delphi list, and meta-analysis along with meta-regression were performed where appropriate.
What was found
Pre-exercise feeding significantly enhanced prolonged aerobic performance (P = .012), but had no significant effect on shorter duration aerobic performance (P = .687). Fasted exercise significantly increased post-exercise circulating free fatty acids (P = .023) compared to fed exercise. Feeding before exercise blunted skeletal muscle and adipose tissue signaling pathways involved in mitochondrial adaptation and substrate utilization. Point estimates and confidence intervals were not reported in the abstract.
Why it matters
The findings demonstrate a clear trade-off: eating before exercise benefits sustained endurance performance, whereas fasting before exercise promotes lipid mobilization and acute adaptive metabolic signaling.
Limits
The abstract omits effect sizes, variance estimates, definitions for exercise duration thresholds (prolonged vs. short), participant characteristics (e.g., training status, sex), and specific findings regarding anaerobic/intermittent performance.
Cited by
- supports Performing longer exercise sessions in a fasted state impairs exercise performance.