Time-restricted eating effects on performance, immune function, and body composition in elite cyclists: a randomized controlled trial

Abstract

Background Although there is substantial interest in intermittent fasting as a dietary approach in active individuals, information regarding its effects in elite endurance athletes is currently unavailable. The present parallel randomized trial investigated the effects of a particular intermittent fasting approach, called time-restricted eating (TRE), during 4 weeks of high-level endurance training. Methods Sixteen elite under-23 cyclists were randomly assigned either to a TRE group or a control group (ND). The TRE group consumed 100% of its estimated daily energy needs in an 8-h time window (from 10:00 a.m. to 6:00 p.m.) whilst energy intake in the ND group was distributed in 3 meals consumed between 7:00 a.m. and 9:00 p.m. Fat and fat-free mass were estimated by bioelectrical impedance analysis and VO2max and basal metabolism by indirect gas analyzer. In addition, blood counts, anabolic hormones (i.e. free testosterone, IGF-1) and inflammatory markers (i.e. IL-6, TNF-α) were assessed. Results TRE reduced body weight (− 2%; p = 0.04) and fat mass percentage (− 1.1%; p = 0.01) with no change in fat-free mass. Performance tests showed no significant differences between groups, however the peak power output/body weight ratio (PPO/BW) improved in TRE group due to weight loss (p = 0.02). Free testosterone and IGF-1 decreased significantly (p = 0.01 and p = 0.03 respectively) in TRE group. Leucocyte count decreased in ND group (p = 0.02) whilst the neutrophils-to-lymphocytes ratio (NLR) decreased significantly (p = 0.03) in TRE group. Conclusions Our results suggest that a TRE program with an 8-h feeding window elicits weight loss, improves body composition and increases PPO/BW in elite cyclists. TRE could also be beneficial for reducing inflammation and may have a protective effect on some components of the immune system. Overall, TRE could be considered as a component of a periodized nutrition plan in endurance athletes. Trial registration This trial was retrospectively registered at clinicaltrials.gov as NCT04320784 on 25 March 2020.

Effect of High-Intensity Interval Training and Intermittent Fasting on Body Composition and Physical Performance in Active Women

“…The absence of significant changes could be due to the fact that the interventions in which a significant reduction in fat mass was observed were of longer duration (>12 weeks) than those used in the present study (8 weeks) [ 49 , 55 ]. Although scientific publications present evidence of changes in body composition regarding fasting as a nutritional strategy in less than 8 weeks for elite male athletes (4-weeeks) [ 56 ], an 8-week duration does not appear to be a sufficient stimulus to promote metabolic flexibility in our study population (active women). Indeed, 4 weeks for active males are not enough to improve the body composition [ 57 ], but 6 weeks was enough to find positive changes in women over 60 years [ 58 ].…”

Efficacy of Popular Diets Applied by Endurance Athletes on Sports Performance: Beneficial or Detrimental? A Narrative Review

“…Studies on IF diets and endurance capacity and performance-related parameters have produced conflicting results in endurance athletes [ 60 , 62 , 64 ]. Both R-IF and TRE studies on endurance athletes stated that IF diets had no influence on the aerobic capacity, determined by VO 2 max [ 60 , 62 , 64 ]. Additionally, one study on TT performance and R-IF in well-trained middle-distance runners showed that R-IF caused a decrease in TT performance [ 60 ].…”

“…However, another study determining the impact of the CHO mouth rising technique on 10 km TT performance declared that the CHO mouth rising technique provided benefits by increasing 10 km TT performance [ 64 ]. For TRE and endurance performance, Moro et al [ 62 ] revealed that a 4 week TRE had no impact on endurance performance. As for evaluating performance-related parameters, several researchers investigated the exercise-induced fatigue, blood lactate, glucose, and insulin concentrations in endurance athletes [ 61 , 63 , 64 , 65 ].…”

“…Studies on IF in endurance athletes have often been conducted during the religious fasting period (R-IF) [60,61,63,64], with few studies investigating the effects of time-restrictive eating (16:8) on endurance performance and health-related effects [62,65]. Fasting diets may alter metabolic pathways in the body by acting as a potential physiological stimulus for ketogenesis [155], regulating metabolic, hormonal and inflammatory responses [61], and stimulating mitochondrial biogenesis and suppressing mTOR activity [155], and regulating body composition [62,65].…”

“…Another aspect of IF is its impact on the body composition of endurance athletes. Studies on endurance athletes and TRE (16:8) revealed that TRE caused a meaningful decrease in BW and body fat percentage in endurance athletes [62,65]. Moro et al [62] claimed that although VO 2 max and endurance performance did not change after a 4 week TRE, a meaningful rise in the peak power output/BW ratio was due to the BW loss.…”