Effects of 8 wk of 16:8 Time-restricted Eating in Male Middle- and Long-Distance Runners.

Time-restricted eating, where all food is eaten within an 8-hour window each day, has become popular among endurance athletes hoping it might help with body composition or performance. This trial looked at whether it actually changes running performance or metabolic health in middle- and long-distance runners. Over eight weeks, runners following the 16:8 pattern were compared with runners eating on their usual schedule, while both groups kept training as normal.

The runners using time-restricted eating lost a small amount of body mass and reported eating less overall, but when it came to running economy, oxygen use, blood lactate, heart rate, or markers like glucose, insulin, and triglycerides, the analysis detected no statistically significant difference between the approaches. This is interesting because it suggests the approach can lower food intake and body mass without an accompanying training or exercise physiology benefit. The trial was small, with only seventeen runners completing it, so these findings should be seen as preliminary rather than definitive.

If you're a runner curious about time-restricted eating, meaning eating all your meals within an 8-hour window each day, this study offers some useful context. Researchers followed a small group of male middle- and long-distance runners for eight weeks, comparing those who used this eating pattern with those who ate on their normal schedule, while everyone kept up their usual training. The runners using the time-restricted approach lost a small amount of body weight and reported eating less food overall.

However, when the researchers looked at running performance measures like oxygen use, running efficiency, and heart rate during exercise, along with blood markers related to metabolic health, they found no statistically significant difference between the two groups. In other words, this eating pattern seemed to reduce food intake and body weight, but there's no evidence from this study that it improved running performance or metabolic health markers. The trial only included seventeen runners who finished it, so these results are a starting point rather than a firm answer, and larger studies would be needed to know more.

This is a summary of research, not medical advice. Talk to your own healthcare provider about anything affecting your care.

This randomised controlled trial examined 16:8 time-restricted eating (TRE) against habitual dietary intake in male middle- and long-distance runners over eight weeks, with 23 randomised and 17 completing (TRE n=10, control n=7). Training load was comparable between groups throughout, which supports interpreting body composition and metabolic changes independent of training volume differences. TRE produced a statistically significant reduction in body mass (mean difference -1.92 kg, 95% CI -3.52 to -0.32, P=0.022) alongside lower self-reported energy intake at mid- and post-intervention (group-time interaction P=0.049).

For the performance and metabolic outcomes, including oxygen consumption, respiratory exchange ratio, running economy, blood lactate, heart rate during exercise, and fasted glucose, insulin, and triglyceride concentrations, the analysis detected no statistically significant difference between the approaches. The small completer sample (n=17) and reliance on self-reported dietary intake are notable limitations that constrain confidence in both the positive body mass finding and the null performance and metabolic findings. Clinicians should note this trial does not establish that TRE enhances endurance performance or metabolic health, only that it may reduce energy intake and body mass without training or immediate physiological trade-offs, and replication in larger cohorts is needed.