Four Weeks of 16/8 Time Restrictive Feeding in Endurance Trained Male Runners Decreases Fat Mass, without Affecting Exercise Performance

Abstract

Background: Time restricted Feeding (TRF) is a dietary pattern utilized by endurance athletes, but there is insufficient data regarding its effects on performance and metabolism in this population. The purpose of this investigation was to examine the effects of a 16/8 TRF dietary pattern on exercise performance in trained male endurance runners. Methods: A 4-week randomized crossover intervention was used to compare an 8-h TRF to a 12-h normal diet (ND) feeding window. Exercise training and dietary intake were similar across interventions. Runners completed a dual-energy X-ray absorptiometry (DXA) scan to assess body composition, a graded treadmill running test to assess substrate utilization, and ran a 10 km time trial to assess performance. Results: There was a significant decrease in fat mass in the TRF intervention (−0.8 ± 1.3 kg with TRF (p = 0.05), vs. +0.1 ± 4.3 kg with ND), with no significant change in fat-free mass. Exercise carbon dioxide production (VCO2) and blood lactate concentration were significantly lower with the TRF intervention (p ≤ 0.02). No significant changes were seen in exercise respiratory exchange ratio or 10 km time trial performance (−00:20 ± 3:34 min:s TRF vs. −00:36 ± 2:57 min:s ND). Conclusion: This investigation demonstrated that adherence to a 4-week 16/8 TRF dietary intervention decreased fat mass and maintained fat-free mass, while not affecting running performance, in trained male endurance runners.

An Intervention of Four Weeks of Time-Restricted Eating (16/8) in Male Long-Distance Runners Does Not Affect Cardiometabolic Risk Factors

“…This report extends the original findings from our TRE study in endurance-trained athletes [ 12 ] in which we observed that the TRE intervention resulted in the loss of total fat mass and body fat percentage with no change in 10 km time trial performance. In the present report, except for discovering a significant decrease in the change in segmental leg fat mass with TRE compared to normal diet, no other changes in segmental body composition, bone mineral content, resting energy expenditure, resting respiratory exchange ratio or cardiometabolic disease markers were found between the TRE and normal dietary interventions.…”

“…We have previously reported [ 12 ] that fat mass significantly decreased by 7% and body fat percentage by 6% in the TRE group compared to no change in the ND group. These changes along with segmental body composition data are reported in ( Table 4 ).…”

“…A normal eating window of 12 h fasting and 12 h eating was modeled after the study designed my Moro, et al to compare results in resistance-trained versus endurance-trained athletes. Details of the study design, subjects and performance testing are provided in Tovar, et al [ 12 ]. Briefly, subjects chose their eating windows and were instructed to consume all caloric intake within the same 12 h or 8 h period during their assigned diet intervention.…”

“…However, none of these studies used a randomized crossover design, and the Brady et al [ 11 ] study did not match calorie or macronutrient contents between interventions. In our companion paper, which examined the effects of 4 weeks of 16/8 time-restricted eating in endurance-trained male runners, we found a significant decrease in fat mass with no change in 10 km time trial running performance [ 12 ]. However, we did not include measures of cardiovascular health in that paper.…”

Effectiveness of Early Time-Restricted Eating for Weight Loss, Fat Loss, and Cardiometabolic Health in Adults With Obesity

“…In our trial, the eTRE group lost an additional 2.3 kg relative to the control group, an approximately 50% improvement in weight loss. For comparison, prior studies are about evenly divided on whether TRE reduces body weight and are mixed for body fat, while studies that shift food intake to the morning and/or earlier in the daytime have more consistently reported weight loss . Of note, a somewhat larger study recently published in the New England Journal of Medicine by Liu et al reported that eTRE was not better for losing weight.…”