24 hours fasting does not impair exercise performance or physiological parameters in CrossFit athletes

Fasting protocols are well known for various health benefits such as increasing metabolic flexibility, improving insulin sensitivity, promoting weight loss, and even slowing down the aging process. In the recent times studies have tested intermittent fasting (IF) in athletes, but its effects on female CrossFit athletes remain relatively unexplored in the existing literature.

A new study in Nutrients journal aimed to evaluate and compare the effects of 24-h IF on the physical performance of female CrossFit practitioners. The study found that 24-h fasting can lead to lower resting blood lactate concentrations, increased post-exercise lactate levels, and higher subjective hunger levels. However, fasting did not significantly affect ratings of perceived exertion, post-exercise blood glucose concentration, handgrip strength, jumping performance, performance times, heart rate parameters, or hydration levels.

Researchers included Eleven female CrossFit athletes (age: 30.91 ± 3.42, weight: 65.26 ± 7.55 kg, height: 1.66 ± 0.05 m) participated in the study. The study used a crossover design with fasting and eating conditions.

The key findings of the study

• Participants completed an exercise test, standing long jump, and handgrip strength assessment. Hydration status, heart rate, blood lactate, blood glucose, rates of perceived exertion, and hunger were measured.

• Results showed significant differences in blood lactate concentration (F = 5.435, p = 0.042, η2p = 0.352). Resting blood lactate concentration was significantly lower in the fasting trial than in the eating trial (p < 0.001), but post-exercise blood lactate concentrations were higher in the fasting trial than in the eating trial (p < 0.001).

• No differences were found in performance times (p > 0.05). In conclusion, this pilot study of females suggests that 24-h fasting does not impair exercise performance or negatively affect physiological parameters in CrossFit athletes.

Researchers concluded that “This pilot study of females suggests that 24-h fasting does not impair exercise performance or negatively affect physiological parameters in CrossFit athletes.”

Reference: Eroglu MN, Rodríguez-Longobardo C, Ramírez-Adrados A, Colina-Coca C, Burgos-Postigo S, López-Torres O, Fernández-Elías VE. The Effects of 24-h Fasting on Exercise Performance and Metabolic Parameters in a Pilot Study of Female CrossFit Athletes. Nutrients. 2023 Nov 20;15(22):4841. doi: 10.3390/nu15224841.