Though there has been a slew of studies on the effects of fasted cardio on exercise performance, the jury is still out on whether skipping breakfast can help or hurt your workout1.
For instance, one study found that exercise performance6 was 3.8% lower in participants who were fasting. Not only that, but energy levels, readiness, pre-exercise motivation, and post-exercise enjoyment also took a dip while fasting. On the other hand, a 2016 study on highly trained endurance athletes found that performance9 was at its peak in the afternoon during Ramadan, while athletes were fasting.
“The research into this question is very young, and we don’t have a lot of high-quality studies to inform us,” explains Steve Hendricks, a journalist, fasting expert, and author of The Oldest Cure in the World: Adventures in the Art and Science of Fasting.
Hendricks also points out that the effects of fasted cardio on performance can vary depending on a handful of factors1, including the length of your fast, the type of exercise that you’re doing, and what your specific goals are, among others.
As an example, one meta-analysis found that eating before exercise had minimal impact on shorter aerobic sessions but could actually enhance performance10 during prolonged workouts. Therefore, adjusting your meal schedule based on your workout may be the best option.
At the end of the day, Hendricks concludes, “the fasted exerciser is likely to improve on some metrics while the fed exerciser improves on others.”
