Fasted cardio or non-fasted cardio?

By Matt Foreman

We have all heard it before that performing low-intensity cardiovascular exercise in a fasted state will utilise fat stores and cause greater fat loss. But this may not be the case after all. Schoenfeld, Aragon, Wilborn, Krieger and Sonmez (1) decided to put this to the test in a lab setting. 

The study published in the Journal of the International Society of Sports Medicine, took twenty young females with recent aerobic training experience and divided them into two groups, fasted and non-fasted. The subjects were all prescribed the same calorie-restricted diet and the same steady-state cardio routine. However, one group would be in a fed state given a shake before performing cardio, and the other would be in a fasted state and consume the shake post cardio. Aragon et al. (1) looked at two main aspects. The amount of weight lost and the amount of body-fat lost.

What did they find?
After 4 weeks, everyone in the study lost body fat. But there was no significant difference between the fasted group and the non-fasted group.

So what does this mean?
One study cannot always be the final say on fasted vs. non-fasted cardio, but if there are benefits to performing fasted cardio, they are extremely minimal. However, another study comparing lipid utilisation over 24hours after completing fasted or non-fasted cardio found that lipid utilisation was actually higher when a meal was consumed before performing cardio compared to being fasted (2).
Due to these results, self experimentation should be used to find what works best for you, but with minimal benefits gained from fasted cardio it may perhaps only be useful for those getting stage-ready in the final weeks when every bit of body fat counts. The main focus however should always be total energy and macronutrient breakdown.

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​References: 

1. Schoenfeld, Brad., Aragon, A., Wilborn, C., Krieger, J., Sonmez, G. (2014).  "Body composition changes associated with fasted versus non-fasted aerobic exercise." Journal of the International Society of Sports Nutrition 11.54 (2014). Accessed December 21, 2014. doi:10.1186/s12970-014-0054-7.

2. Paoli, A., Marcolin, G., Zonin, F., Neri, M., Sivieri, A., Pacelli, QF. (2011). Exercising fasting or fed to enhance fat loss? Influence of food intake on respiratory ratio and excess postexercise oxygen consumption after a bout of endurance training. International Journal of Sport Exercise Metabolism. 2011 Feb;21(1):48-54.