Should you do your cardio in a fasted state?
Should you do your cardio in a fasted state?
Occasionally, we get asked whether someone should do their cardio in a fasted or fed state? There’s a belief out there that cardio should be done on an empty. However, the research doesn’t really back this. That said, here’s a recap on a couple of those studies:
In one study, 20 healthy young women were each given an individualized, calorie-restricted meal plan. The women were then divided into two groups. One did fasted cardio while the other did so after a meal. Both groups performed an hour of cardio, which included a 5 minute warm-up and cool down at 50% maximal heart rate (MHR) and 50 minutes of steady-state cardio at 70% (MHR). They did this 3 times a week in the morning for 4 weeks.
The results showed that both groups lost weight and fat mass with no significant difference between them. Enter study #2.
In this second study, 16 overweight women were divided into two groups. Just like in the first study, one group did fasted cardio while the other did it fed. The difference in this study is that the cardio performed was high intensity interval training (HIIT). (Note: HIIT basically has you cycle between periods of low- and high-intensity effort.) Each session consisted of 10 intervals with 60s of high-intensity effort (around 90% maximal heart rate) and 60s at a low intensity. Both groups performed HIIT three times a week for 6 weeks. The result? Both groups lost fat and gained muscle with no significant difference between groups.
So whether you choose to do steady-state cardio or HIIT in a fed or fasted state, doesn’t seem to matter in regards to fat loss. What does matter is that you do it. Just keep in mind that we generally recommend people limit cardio when trying to lose fat – just enough to see results.
And now you know. 
:-)
Study #1: Schoenfeld, BJ et al. Body composition changes associated with fasted versus non-fasted aerobic exercise. J Int Soc Sports Nutr. 2014. 11:54.
Study #2: Gillen, JB et al. Interval training in the fed or fasted state improves body composition and muscle oxidative capacity in overweight women. Obesity (Silver Spring). 2013. Nov;21(11):2249-55.