Effects of fasted vs fed‐state exercise on performance and post‐exercise metabolism: A systematic review and meta‐analysis

Abstract

The effects of nutrition on exercise metabolism and performance remain an important topic among sports scientists, clinical, and athletic populations. Recently, fasted exercise has garnered interest as a beneficial stimulus which induces superior metabolic adaptations to fed exercise in key peripheral tissues. Conversely, pre-exercise feeding augments exercise performance compared with fasting conditions. Given these seemingly divergent effects on performance and metabolism, an appraisal of the literature is warranted. This review determined the effects of fasting vs pre-exercise feeding on continuous aerobic and anaerobic or intermittent exercise performance, and post-exercise metabolic adaptations. A search was performed using the MEDLINE and PubMed search engines. The literature search identified 46 studies meeting the relevant inclusion criteria. The Delphi list was used to assess study quality. A meta-analysis and meta-regression were performed where appropriate. Findings indicated that pre-exercise feeding enhanced prolonged (P = .012), but not shorter duration aerobic exercise performance (P = .687). Fasted exercise increased post-exercise circulating FFAs (P = .023) compared to fed exercise. It is evidenced that pre-exercise feeding blunted signaling in skeletal muscle and adipose tissue implicated in regulating components of metabolism, including mitochondrial adaptation and substrate utilization. This review's findings support the hypothesis that the fasted and fed conditions can divergently influence exercise metabolism and performance. Pre-exercise feeding bolsters prolonged aerobic performance, while seminal evidence highlights potential beneficial metabolic adaptations that fasted exercise may induce in peripheral tissues. However, further research is required to fully elucidate the acute and chronic physiological adaptations to fasted vs fed exercise.

Is exercise best served on an empty stomach?

“…There is little doubt that the investigation of how nutrient intake in and around exercise might modulate the metabolic, molecular and adaptive responses to exercise training is of major current interest (9,10,23,(49)(50)(51) . However, there is a need for further research in order to fully elucidate if overnight-fasted exercise could be a means to optimise the health benefits of physical activity.…”

ADORA2A C Allele Carriers Exhibit Ergogenic Responses to Caffeine Supplementation

“…Finally, to avoid any potential confounding by prior food and caffeine ingestion [40,41], we opted to test the participants in a fasted state. This needs to be acknowledged as a limitation given that caffeine supplementation and exercise in a fasted state is likely not a "real-life" practice of many individuals, and is not in line with the current sports nutrition recommendations [42]. Future studies may consider further exploring this topic by using caffeine supplementation protocols that mirror those more commonly observed in practice.…”

Effects of fasting on the expression pattern of FGFs in different skeletal muscle fibre types and sexes in mice

“…Fasting and fed conditions divergently influence skeletal muscle structure and metabolism [36]. In this study, we found that fasting influenced expressions of Fgfs in mouse skeletal muscle.…”