Is Intermittent Fasting Useful for Athletes?

Check out this answer from Consensus:

Intermittent fasting, particularly time-restricted feeding, can be useful for athletes by improving aerobic capacity, aiding in weight loss, and offering additional health benefits. However, the effects on performance can vary depending on the type of fasting and individual responses. While TRF appears to be beneficial, Ramadan intermittent fasting may impair aerobic performance. Overall, IF can be a valuable component of an athlete’s nutrition plan, especially when carefully managed to ensure adequate energy and nutrient intake.

Intermittent fasting (IF) has gained popularity among athletes for its potential benefits on body composition and performance. This dietary practice involves alternating periods of eating and fasting, and it includes various protocols such as time-restricted feeding (TRF) and Ramadan intermittent fasting (RIF). The question of whether IF is useful for athletes is complex and depends on multiple factors, including the type of fasting, the sport, and individual responses.

Key Insights

• Improvement in Aerobic Capacity with TRF:
  • Time-restricted feeding (TRF) protocols have been shown to significantly enhance maximum oxygen uptake (VO2 max), which is a critical measure of aerobic capacity1 3.
• Weight Loss and Body Composition:
  • IF, particularly TRF, can lead to reductions in body weight and fat mass while maintaining or slightly improving fat-free mass. This can be beneficial for athletes in weight-restricted sports3 4 5 10.
• Mixed Effects on Performance:
  • While TRF may improve aerobic capacity, Ramadan intermittent fasting (RIF) has been associated with reduced aerobic performance. However, the effects on muscle strength and anaerobic capacity are generally non-significant1 6 9.
• Potential Benefits Beyond Weight Loss:
  • IF may offer additional health benefits such as reduced systemic inflammation, improved metabolic health, and better immune function, which can indirectly support athletic performance2 3 4.
• No Significant Decrease in Performance:
  • Studies indicate that IF does not significantly decrease performance in various sports, including endurance and combat sports, provided that athletes maintain their energy and macronutrient intake during eating periods6 9 10.
• Individual Variability and Adaptation:
  • The impact of IF on performance can vary among individuals. Some athletes may experience subjective feelings of fatigue and mood changes, but these do not necessarily translate to decreased performance8 9.

Is intermittent fasting useful for athletes?

Asma Aloui has answered Uncertain

An expert from University of Gafsa in Sports Science, Exercise Physiology

There is a perpetual concern over athletes’ nutrition and the impact of intermittent fasting on their performance. Most of the studies looking at performance and fasting are regarding athletes who observe Ramadan. Looking at high-intensity, endurance, and resistance exercises, studies have been varied but are uniform in showing that there is no benefit to athletic performance while fasting. For more details, you can read this recent paper:

Levy, E., & Chu, T. 2019. Intermittent fasting and its effects on athletic performance: A review. Current Sports Medicine Reports, 18(7), 266-269.