Abstract
BackgroundAlthough 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.MethodsSixteen 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.ResultsTRE 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.ConclusionsOur 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 registrationThis trial was retrospectively registered at clinicaltrials.gov as NCT04320784 on 25 March 2020.
Highlights
A proper nutrition strategy is an important aspect of elite sport physical training, as nutrient availability can influence energy expenditure, body composition, and performance, and the immuno-response to exercise
We have recently demonstrated that 8 weeks of time-restricted eating (TRE) does not impair muscular performance improvements in young untrained individuals performing resistance exercise training [20], can decrease fat mass and improve some health-related biomarkers (i.e. IL-6, tumor necrosis factor-α (TNF-α), Insulin, high-density lipoprotein cholesterol (HDL-C), TG) in resistance-trained males [21], and does not impair lean mass gain or performance improvements in resistance-trained females [22]
Body composition After 4 weeks, a significant time x diet interaction (p = 0.04) was observed in total body weight: the TRE group experienced a significant (p = 0.03) decrease total body mass of ~ 2% while no significant change was observed in the Normal Diet (ND) group
Summary
A proper nutrition strategy is an important aspect of elite sport physical training, as nutrient availability can influence energy expenditure, body composition, and performance, and the immuno-response to exercise. IF is not a popular strategy and is mainly linked to those athletes that follow the Ramadan restriction, in which the caloric consumption is allowed only during nighttime with a great influence on the circadian rhythm, hormonal regulation and thermoregulation due to a limited fluid intake [6, 7]. Authors remarked that reduced physical performance during Ramadan may be caused by sleep disturbance and dehydration, and that these effects seem to be more pronounced in amateur than elite athletes. 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
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