Fasted Cardio : Does it burn more fat?


I used to think fasted cardio did more for my body than just good ol’ fashioned cardio on a nice full, happy stomach. Mainly just because I was suffering more and somehow I thought that meant more success.. ?

The theory is this- normally, your body uses your glycogen stores (the carbs it stores for energy) to get you through cardio. When you’re on an empty stomach, these stores are empty and so your body says, “Okay, cool I guess I’ll use the fat then.” This is how people are led to believe that they’re going to burn more fat if their cardio is fasted.

Here are the catches-

1. Remember that you burn post workout too! And your body is smart. It keeps the ratio of fat/carb burning pretty balanced. Essentially, if you burn more fat during your workout, when you feed your body after, it will burn the carbs then instead. So either way, you’ll burn both. It’s just a matter of how much you feel like suffering that day..

2. If your body doesn’t have carbs to use during your workout, it isn’t just going to hit up your fat for energy. It’s going to dig into your available protein as well! This takes away from your ability to preserve and build your muscles! Not only that, but protein is used by your body for several other important processes including tissue repair throughout the entire body and cell turnover. If your protein is being used as your energy source for exercise, your body may not have what it needs to perform these functions optimally - especially if you’re dieting down.

3. You will likely experience bonking, which is the nice scientific term for your glycogen stores being depleted and, therefore, causing you to suffer through very low energy levels. If your energy is very low, you likely won’t burn more simply because you won’t be able to perform optimally. Your strength and endurance will suffer and so will your calorie burn.

There are certainly times where it makes sense to do your cardio fasted. Some people choose to perform their cardio fasted due to convenience. They get their cardio done first thing in the morning before work, and heading straight to the gym just ensures that they have enough time. Other people prefer their cardio fasted because they find it uncomfortable to do intense cardiovascular activity on a full stomach. This is perfectly fine! In fact, in these cases, it’s better because it’s more sustainable for these individuals.

In every case, the best strategy for weight loss and fat burn is always the one that feels most sustainable for you. I personally run fasted first thing in the morning. This is not because I believe I’m going to burn more. Rather, doing my runs fasted simply ensures that they actually happen… it allows me to get my cardio done without the threat of getting distracted in the morning or coming up with excuses for why I can’t do it. It’s essentially my “roll out of bed” technique for sticking to my commitments - just get it done before I have time to think about it and decide that I actually don’t want to.

There is absolutely a time and place for fasted cardio in your routine. Just do not rely on fasted cardio as a way to increase your fat burn over performing regular cardio. Moral of the story here is if you’re cranky hopping on the treadmill without breakfast, then DON’T. You don’t have to. Trust me, you’re not missing out on anything..


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