So, the competition season is just around the corner, and you’re wondering about cardio (if you’re not, you should be). The most frequently suggested advice for getting rid of body fat is doing cardio on an empty stomach as soon as you wake up. From celebrities to fitness gurus, everyone seems to be advocating this type of cardio, so I thought I’d delve into it a little further.
The theory behind fasted cardio is that your body conserves its carb (glycogen) stores during sleep, while you’re fasting overnight, and starts to mobilize fat instead to be used as fuel. So, why not take advantage of this opportunity where your body is in a ready state to burn some fat? There are a few other things to take into account before we all start going crazy and running around in the morning.
Most of the research that supports fasted cardio mainly focuses on how many calories are burned during exercise. If the exercise is typical cardio (jogging/walking/cycling), some studies suggest that performing these on an empty stomach, you may burn up to 20% more calories than if you ate beforehand. However, the word “during” exercise is problematic due to the fact that the real benefits of exercise follows training. In other words; high intensity training (including weight lifting and HIIT) burns more calories (and fat) in total (during and after exercise) than low-intensity cardio (calorie burn mainly during the exercise). So, a 15 minute HIIT session can outweigh an hour or more of walking and jogging.
But, to perform at high intensity you need to have sufficient fuel! I’ve tried training legs first thing in the morning, in order to benefit from the fasted state and doing high intensity training. It didn’t work: felt light-headed after first couple of sets and had to give up. You know the feeling when you want to throw up, but there’s nothing in your stomach to throw up? Horrible feeling, you don’t need to experience it again! Trust me; I’ve tried this stupid idea more than once with the same result. To get the most out of my training and not gas-out half way through I need to have ate something a couple of hours beforehand.
While the fasted state does reserve your glycogen stores and activate your fat stores, it also tends to mobilize more amino acids for fuel. In other words, exercising in a fasted state can tap into your muscle stores for fuel as well, which is definitely not something you want unless you don’t care about muscle mass or have too much (is there even such thing?). If your sole focus is muscle preservation while trying to lose body fat, I’d suggest avoiding cardio on an empty stomach.
If you have a hectic schedule and have to do cardio or training in the morning (or you just prefer training in the morning as opposed to afternoon), I usually suggest having low GI carbs the night before, then having some sort of amino acids before the actual cardio, whether that is BCAA’s, EAA’s or Hydrolysed Protein. However, I have met people that perform better in a fasted state than they do in a fed. So, the fasted cardio dilemma is very subjective!! As you’ve figured out by now there are no definite rules for fitness, every body is different and what works for some might not work for others. Articles I’ve read from other fitness gurus advocate low-intensity cardio in a fasted state if you’re already lean (below 10% for males and below 15% for females) in order to get leaner and tap into the more stubborn fat deposits, followed by a protein shake.
REVIEW: Fasted Cardio
Pros: Body is primed for burning fat, up to 20% more fat loss, great for lean individuals looking to get leaner.
Cons: May burn some muscle, total calories burned are outweighed by HIIT, lack of intensity during training.
If you’re getting ready for a body-building competition, do not worry about fasted cardio in the initial stages of your prep. Your aim here is to conserve muscle and burn fat, so stick to HIIT sessions a few of times per week instead. 2 to 4 weeks out of competition start throwing in a morning fasted cardio session every now and then to take advantage of the pros listed above. Also, having a morning exercise session and one in the afternoon gives your body two metabolic spikes: another advantage when trying to lose body-fat.
On the other hand, if your main goal is to lose weight in general (not worrying about body fat %) then stick to HIIT sessions throughout your transformation as the total calories burned outweigh the benefits of fasted cardio.