Fasted Cardio for Fat Loss – Overrated or Accurate?

Sep 08, 2022

When it comes to losing body fat, you’ll find many a bodybuilder, influencer and coach preaching about fasted cardio and the benefits for fat loss.

And there are benefits – cardio of course is going to increase your energy expenditure over the week. This can accelerate your rates of fat loss, and / or potentially allow you to eat a little bit more food during your fat loss phases.

However, does it matter if you perform the cardio before or after eating?

For fat loss, no!

See, the misconception likely comes past research that found cardio when done in a fasted state uses more fat for energy (2016 Study)

This is because without a recent influx of dietary carbohydrates in our system to draw glucose from, our body can preferentially use fat for aerobic activity.  However, the issue here is that this isn’t likely going to influence body composition any more than fed cardio using carbohydrates for energy.

This is because preferentially burning more fat for fuel differs to the bodily process which leads to a decrease in your body fat levels.

So, when it comes to fat loss, what is the driver of this process will always be the distortion of energy balance to create a calorie deficit.

And a 2014 study by Schoenfeld et. al heavily backs this claim up.

The study took 20 women and assigned them into two groups. One group would exercise fasted and the other would exercise fed, performing one hour of aerobic activity three times per week.

They then measured their body composition throughout, finding there to be no significant difference in body composition changes between the two groups.

I’d also argue that performing cardio while fasted, can potentially impact your training performance and energy cost for the session.  Granted, if your cardio is solely a brisk walk, this impact would probably be minimal if at all, but if you’re performing higher intensity cardio, you may find a drop off in your work capacity.

Lower performance and effort during exercise = lower calories burnt.

Yet, if you prefer to perform your cardio fasted this is totally fine too! However, what dictates fat loss is and will always be a net deficit of calories, not whether you’ve eaten beforehand or not.