Exercise Running on Empty-The Science Behind Fasted Cardio

fasted cardio

Discover the insightful analysis and practical implications of fasted cardio for fat loss in part two of my ongoing series on fitness and nutrition literature.

Summer is approaching, and the desire to achieve a ripped physique for beach season, like the temperature, is rising. Among the various fitness strategies, fasted cardio has gained popularity as a way to maximize fat loss. But does it truly live up to the hype? Do you need to “run on E” to get shredded? Let’s explore scientific research to uncover the truth.

The Science 

Recent and past studies conducted by Liu et al. (2023) and Proeyen et al. (2010) have revealed that whether individuals engage in fasted cardio or consume food beforehand, there is minimal difference in overall fat loss. These findings challenge the notion that fasted cardio is significantly more effective. However, fasted cardio does offer certain advantages beyond fat loss. It has been shown to improve glucose tolerance, which is particularly beneficial for individuals with metabolic disorders such as diabetes, hyperthyroidism, hypothyroidism, or gout.

When it comes to building muscle mass, a study conducted by Gillen and colleagues in 2013 found that people who ate before doing cardio exercises had slightly more muscle growth compared to those who did cardio on an empty stomach. It’s important to note that this study specifically looked at overweight or obese sedentary women, so the findings may not apply to everyone.

Another study conducted by Schoenfeld et al. (2014), involving untrained women on a reduced-calorie diet, revealed no significant differences in fat loss between individuals who performed fasted cardio and those who exercised after eating. Therefore, for most people, engaging in cardio on an empty stomach may yield little variations in fat loss outcomes.

However, for bodybuilders or already pretty lean people that want to maintain their muscle while losing that last little bit of fat, it may be beneficial for the anabolic environment to have a protein-containing meal before doing cardio, as suggested recommendations made by Escalante and Barakat (2020).

My Thoughts in Layman’s Terms

Simply put, if you’re trying to build or maintain muscle and you’re not overweight or obese, eating something before doing cardio exercises could help you see better results. This is especially true for those who are already lean and want to preserve their muscles while getting rid of excess fat. A protein snack before cardio can fuel your muscles and support their growth during exercise. Remember that these findings may not apply to everyone, and individual preferences and goals should be considered when deciding whether or not to eat before cardio.

We also need to acknowledge individual preferences and circumstances. Feeling better and more motivated while performing fasted cardio is unlikely harmful and may help you adhere to your exercise routine. Additionally, individuals with metabolic concerns have found promising results in improved glucose tolerance and overall metabolic health when incorporating fasted cardio under the care and direction of qualified healthcare providers.

While fasted cardio may not profoundly impact fat loss for most individuals, it can be advantageous in specific scenarios. Those aiming to maintain muscle while losing fat may benefit from consuming a protein snack before cardio sessions. Ultimately, finding what works best for your goals and personal preferences is key to achieving success in your fitness journey.



Gillen, J. B., Percival, M. E., Ludzki, A., Tarnopolsky, M. A., & Gibala, M. J. (2013). Interval training in the fed or fasted state improves body composition and muscle oxidative capacity in overweight women. Obesity (Silver Spring, Md.), 21(11), 2249–2255. https://doi.org/10.1002/oby.20379

Guillermo E, Barakat C. (2020). Fasted versus nonfasted aerobic exercise on body composition: considerations for physique athletes. Strength and Conditioning Journal. 2020 Oct;42(5):71-78.

Liu, X., He, M., Gan, X., Yang, Y., Hou, Q., & Hu, R. (2023). The Effects of Six Weeks of Fasted Aerobic Exercise on Body Shape and Blood Biochemical Index in Overweight and Obese Young Adult Males. Journal of exercise science and fitness, 21(1), 95–103. https://doi.org/10.1016/j.jesf.2022.11.003

Schoenfeld, B. J., Aragon, A. A., Wilborn, C. D., Krieger, J. W., & Sonmez, G. T. (2014). Body composition changes associated with fasted versus non-fasted aerobic exercise. Journal of the International Society of Sports Nutrition, 11(1), 54. https://doi.org/10.1186/s12970-014-0054-7

Van Proeyen, K., Szlufcik, K., Nielens, H., Pelgrim, K., Deldicque, L., Hesselink, M., Van Veldhoven, P. P., & Hespel, P. (2010). Training in the fasted state improves glucose tolerance during fat-rich diet. The Journal of Physiology, 588(Pt 21), 4289–4302. https://doi.org/10.1113/jphysiol.2010.196493

Team Basix By: Back To The Basix

Comments are closed