DCU research finds that intermittent fasting could help long distance runners go that extra mile
A study led by DCU has found that the use of intermittent fasting has the potential to provide middle and long distance runners with an extra boost in their performance by bringing about a small drop in body weight.
The study is the first of its kind to investigate the effect of a period of intermittent fasting (IF) in the form of the popular method of 16:8 (16 hours fasting/8 hours eating) in an endurance trained population. This approach, also known as Time-Restricted Eating (TRE), has become popular in the general population in recent years, but in athletic populations has only previously been studied in strength training individuals and mixed effects have been reported.
This new DCU-led TRE study, undertaken by 23 male middle and long distance runners, found there was no positive or negative impact on the measurements associated with endurance running performance or metabolic health. However, TRE did produce a decrease in body weight of approximately 1.5% (or 1.1 kg) in 8 weeks in line with a reduction in daily calorie intake. Crucially, the reduction in daily calorie intake was due to spontaneous rather than deliberate calorie cutting actions by the participants.
The research paper “Effects of Eight Weeks of 16:8 Time-restricted Eating in Male Middle- and Long-Distance Runners” is published in the Medicine & Science in Sports & Exercise, the flagship journal of the American College of Sports Medicine and was led by Aidan Brady and Dr Brendan Egan at the DCU School of Health and Human Performance.
According to Dr. Egan, “Despite a lot of interest amongst athletes in novel approaches to nutrition including intermittent fasting and time-restricted eating, this was the first study of its kind to explore the 16:8 approach for effects on measures such as body weight and performance in endurance athletes.”
The research involved an eight week assessment of TRE in parallel with regular exercise training. The purpose was to investigate the effects of TRE on body composition, energy and macronutrient intakes, indices of endurance running performance and markers of metabolic health in endurance athletes.
The results were not unexpected, says Dr. Egan,
“There have been several studies on members of the general population that suggest that if people shorten the so-called feeding window on a daily basis that there is generally a reduction in calorie intake, all other things being equal. With the athletes in our study continuing to exercise at this time, the loss in body weight was not surprising. However, whether this pattern continues for longer than the 8 weeks of our study, or whether other compensatory behaviours begin to bring calorie intake or body weight back up to where it started remains to be seen.”
Of the 23 male middle and long distance runners, who trained on average five times per week, 12 were randomly assigned to the TRE intervention and the remainder followed their usual pattern.
The TRE group consumed all of their calories within an 8 hour eating window of their choosing. Most importantly, the group followed their usual dietary patterns and food choices, with the only change being that they had to eat their calories within the 8 hour window each day.
They also continued to follow their usual training plan during the course of the study.
They completed an incremental exercise test before and after the 8 week intervention, which assessed their respective blood lactate concentrations, running economy and maximal oxygen uptake. The study also found that there was no significant impact of TRE on oxygen consumption during training, running economy or heart rate, among the components checked for. In other words, performance was not impacted positively or negatively during the study period.