• Emma

Does Fasted Cardio Burn More Body-Fat?

Updated: Jun 25, 2018

It is often claimed that doing cardio on an empty stomach will help you burn for fat...e.g fasted....

Acutely this is true.

With less immediate carbohydrate availability your body turns to fat for energy.

So, DURING exercise you will use more fat for fuel when you exercise fasted compared to exercising after a meal. 

However, the real question is..Does doing cardio fasted mean you lose more body fat?

And it seems that no it doesn't. 

One study set to test this included 20 dieting females who were split into fasted cardio (no food before) or fed cardio (having eaten before) experimental groups. 
After 4 weeks of fasted or non fasted cardio body composition changes were measured and although both groups lost fat over the 4 weeks there was no significant differences between either of the groups.

This indicates that it is the calorie balance at the end of the day that determines fat loss and whether you do your cardio fasted or fed is irrelevant. 

So, from a physiological perspective there doesn't seem to be any meaningful effect of fasted cardio on fat loss. 

But what about from a behavioural perspective?

Where fasted cardio may benefit fat loss


1) If you eat less because of it - If doing fasted cardio means you miss breakfast and then only have time for a quick shake before work, this could reduce your daily calorie intake that day.

2) If it fits into your daily routine well - Maybe you wouldn't make time for the gym if you had to eat breakfast before hand.

Where being fasted may be detrimental to fat loss:

1) If not eating prior to exercise impacts your exercise performance - If your too hungry to finish your full session or you exercise at a lower intensity because you feel less energetic - this can impact the calories you burn during your work out. 

2) If doing cardio first thing in the morning doesn't suit your lifestyle - thus trying to fit it in impacts overall adherence.

Take home:

Energy balance is the key to fat loss.

The amount of fat you lose is dependent on the calories you do (or don't) consume and do (or don't) expend, not on whether or not you do your cardio fasted.

If fasted cardio fits into your life and you enjoy it then there is no reason to avoid it. If you absolutely hate getting up in the morning or struggle to exercise as hard without consuming food before hand then do your cardio in a fed state.