Fasted cardio was a huge fad for a long time, then I think it faded out, but I still see people doing it most of the time during contest prep.
Many may not know what fasted cardio is. I remember the first time I heard about it, I had no idea. It's cardio when you first wake up in the morning before you have anything to eat.
Sounds miserable right? Ha. You all know that I'm a fan of cardio, but I am not a fan of fasted cardio. The point of it is that it's supposed to burn fat more because when you wake up after 8-10 hours without anything to eat, your body tends to use fat for fuel and conserves carb energy sources. This way, it burns more fat and the studies have shown that this is the case. Also the idea is that if you eat before then you are going to have to work that off before you tap into fat storage. Essentially, this is true.
Before, I go any further, I would like to just give my practical point of view. If you are a bodybuilder and you are looking to cut the last bit of fat towards the end near a show then by all means, if you feel it's necessary, do fasted cardio and you might see minimal differences. However, if you are just on a plan for every day then honestly, why torture yourself? It's not worth it. Cardio is going to be effective if it's done.
You also have to look at the fact that most of the time, people are going to do steady state cardio when they do fasted. Time and again, HIIT (high intensity interval training) is shown to be more effective for fat loss so why not just do HIIT later in the day. Again, let's be practical. If you have tons to do and the only time that you can go is in the morning, then sometimes, people get sick if they try to eat beforehand. Well then, on accident, you will end up doing cardio fasted. However, I never ever recommend lifting weights on an empty stomach. If you are lifting, then you are wanting to gain muscle correct? Just as your body is going to use fat for fuel, it is also going to use some amino acids as well which are the building blocks of protein aka WASTED GAINS! hehe!
There are also researchers that have stood by the fact that fasted cardio does show increased fat loss in the beginning of the day when you are doing the actual exercise but what about during a given day. Essentially, burning calories is the name of the game for weight loss and if you are burning the same amount of calories and eating in a caloric deficit, then your body is going to lose weight. When your body is "filled" with something, then the rest spills over. If you wake up and your body utilizes fat in that workout, then that means that your glucose is filled up. So doesn't that mean that once you eat carbs, this is going to spill over, and guess what?... Be stored as fat.
Also, people will argue that it continues to burn more calories throughout the day. Okay, not to be a debby downer but most people who are doing fasted cardio are doing a little jog on the treadmill for 25-30 minutes. The data shows that the amount of fat burn post workout from this is essentially negligible.
So, why am I a fan of cardio? I actually hate that word. I know that's silly but I just think it sounds so.....non athletic. I am a fan of cardio because I'm a fan of being an athlete. I'm a fan of being a well rounded athlete. I am not concerned about fat loss, however since we are on the subject of cardio and fat loss, marathon training is not for you.
I think many times people start training for long races because running=weight loss right? No. The amount of training that is required is going to produce a lot of cortisol (stress hormone) and in some cases, with extra nutrition, marathon runners will gain weight during training.
I know that I have not provided you with every detail of research behind fasted cardio, but I simply wanted to give you my logical opinion in that I just don't think that it's going to make that big of a difference and most people absolutely hate doing it, so I just don't see the utility especially in everyday people not bodybuilders.
With love and cardio,