You may have heard that your a.m. cardio session will help you burn a lot more fat if you do it on an empty stomach, but scientifically speaking can this really be true? There is much debate on this. I have my opinion ; however, with the pros and cons I am about to give you, you will have to come up with your opinion as well.
So let’s look at the pros to fasted cardio:
1. First of all you don’t have to wake up earlier to eat and digest your meal which is a major plus on my opinion.
2. Some studies show that you can burn 20% more fat ( this will be challenged in a minute).
3. There is a possible increase in VO2 max (the highest amount of O2 someone can use).
4. Overnight your body reserves carbs and breaks amino acids into glucose allowing the body to shuttle around the fat and amino acids.
5. In the morning, cortisol levels are high and insulin levels are low. Cortisol breaks down tissue (fat) and since the insulin levels are low ( high insulin slows fat metabolism) cortisol is more effective at breaking down that fat.
So far it sounds like a win right? Wait and see the cons before coming to your conclusion:
1. Not surprisingly you will have less energy during a fasted workout, so you won’t be hitting it as hard. This is especially important if you are doing a HIIT or interval workout that focuses and short intense bursts. In fact, the fat is broken down so quickly during a fasted HIIT workout that it actually goes back into the fat cells post workout. That just doesn’t seem fair I know.
2. Some reports say that your body breaks down more protein (muscle) than fat in a fasted state. If it is a lean physique you are after this could be detrimental to your weight room efforts.
3. A pre-workout meal has been shown to raise the afterburn after a workout.
Now to bring this altogether, I must emphasize that our focus is on fasted cardio – not weight training. A weight training session should not be done on an empty stomach as you need maximum energy to put forth the effort your muscles need to change.
To sum it up, in my opinion the occasional fasted cardio workout is ok. I am a big believer in challenging your body on a constant basis in order to see change, and I certainly wouldn’t do all of my cardio sessions fasted (especially the intense intervals).
Also, some mornings it is nice to wake up (have a cup of coffee of course), get my steady state run in and leave the rest of my day for other things.
That is my take on it, so what are your thoughts?