The effects a particular kind of short term fasting called time restricted feeding (TRF) have been recently investigated on resistance training athletes; no data are available, instead, on endurance athletes.
PURPOSE: We sought to investigate the effects of 4 weeks of 16/8 TRF (with windows of 16 hours of fasting and 8 hours of feeding) on elite cyclists.
METHODS: 16 elite under-23 cyclists were randomly assigned to a TRF group or to a control group (CTRL) with a traditional meal pattern. The TRF group consumed 100% of its estimated daily energy needs in an 8-hour time window: from 10:00 AM to 6:00 PM whilst the CTRL group consumed 100% of its estimated daily energy needs in 3 meals between 7:00 AM and 9:00 PM. During the experimental period, training loads were similar in the two groups. Athletes were tested before and after 4 weeks of the intervention. Fat and lean body mass were measured by bioelectrical impedance analysis, VO2max and basal metabolism were measured by indirect gas analyzer. In addition, blood counts, free testosterone, SHBG, IGF-1, IL-6, TNF alpha, VES, PCR, total cholesterol, triglycerides, TSH, free T3, insulin, adiponectin, and cortisol were measured.
RESULTS: After 4 weeks, there was a significant decrease of body weight (TRF: -1.26 kg ± 1.57 vs. CTRL: +0.22 ± 0.96 kg, p=0.038) and fat mass in the TRF group (p=0.0093) compared to CTRL group with no differences in lean body mass. Performance tests showed no significant differences between groups even though there was a significant increase in the peak power output/body weight ratio (p=0.024) in the TRF group due to weight loss. Free testosterone and IGF-1 decreased significantly (p=0.004 and p=0.048 respectively) in the TRF group; leukocyte count decreased more in the CTRL group (p = 0.039). Lymphocyte count increased in TRF group (p<0.001) whilst neutrophils decreased in both groups (p<0.001), thus the neutrophils to lymphocytes ratio (NLR) decreased significantly (p=0.003) in TRF group. No significant changes in other blood chemistry values were observed.
CONCLUSIONS: Our results suggest that a TRF program with an 8-hour feeding window causes fat loss, maintains lean mass and performance indexes and improves peak power output/body weight ratio. The changes of white blood cells parameters worth further investigation.