Exercise Training and Fasting: Current Insights

Abstract

Hassane Zouhal, 1 Ayoub Saeidi, 2,* Amal Salhi, 3,* Huige Li, 4 M Faadiel Essop, 5 Ismail Laher, 6 Fatma Rhibi, 1 Sadegh Amani-Shalamzari, 2 Abderraouf Ben Abderrahman 7 1M2S (Laboratoire Mouvement, Sport, Santé), University of Rennes, Rennes F-35000, France; 2Department of Exercise Physiology, Faculty of Physical Education & Sports Science, Kharazmi University, Tehran, Iran; 3Department of Medicine Physical and Functional Rehabilitation of the National Institute of Orthopedics “M.T. Kassab”, Tunis, Tunisia; 4Department of Pharmacology, Johannes Gutenberg University Medical Center, Mainz, Germany; 5Cardio-Metabolic Research Group (CMRG), Department of Physiological Sciences, Stellenbosch University, Stellenbosch 7600, South Africa; 6Department of Anesthesiology, Pharmacology & Therapeutics, Faculty of Medicine, The University of British Columbia, Vancouver, Canada; 7Higher Institute of Sport and Physical Education, Ksar-Said, University of Manouba, Manouba, Tunisia*These authors contributed equally to this workCorrespondence: Hassane ZouhalM2S (LaboratoireMouvement, Sport, Santé), University of Rennes, EA 1274, Rennes F-35000, FranceEmail [email protected]: Fasting is defined as the abstinence from consuming food and/or beverages for different periods of time. Both traditional and modern healthcare systems recommend fasting as a therapeutic intervention for the management of several chronic, non-infectious diseases. Exercising during a fasting state increases lipolysis in adipose tissue while also stimulating peripheral fat oxidation, resulting in increased fat utilization and weight loss. A key focus of this review is to assess whether endurance training performed while fasting induces specific training adaptations, where increased fat oxidation improves long-term endurance levels. Fasting decreases body weight, lean body and fat content in both trained and untrained individuals. Several studies indicate a broader impact of fasting on metabolism, with effects on protein and glucose metabolism in sedentary and untrained subjects. However, there are conflicting data regarding the effects of fasting on glucose metabolism in highly trained athletes. The effects of fasting on physical performance indicators also remain unclear, with some reporting a decreased performance, while others found no significant effects. Differences in experimental design, severity of calorie restriction, duration, and participant characteristics could, at least in part, explain such discordant findings. Our review of the literature suggests that there is little evidence to support the notion of endurance training and fasting-mediated increases in fat oxidation, and we recommend that endurance athletes should avoid high intensity training while fasting.Keywords: fasting state, calorie restriction, metabolic adaptation fat oxidation, glucose metabolism, endurance performance, Ramadan

Keywords

• fasting state
• calorie restriction
• metabolic adaptation fat oxidation
• glucose metabolism
• endurance performance
• ramadan.