The Ins & Outs of Fasted Cardio


Fasted Cardio. You’ve heard the term, but what does it actually mean?

The basic idea behind fasted cardio is that you’ll get up before downing your usual breakfast, head to the gym and get on the treadmill for a good 45-60 minutes in hopes of using fat stores for energy rather than the food you just ate.

Some people love the idea, some hate it. Some simply turn their noses up at running on empty.

In order to comprehend how cardio on an empty stomach could be beneficial, we first need to understand why it would work.

What is Fasted Cardio?

Your body is in a fasted state upon waking, before consuming your first meal of the day. During this fasted state, your body’s natural levels are optimal for fat loss. After not eating for the last 10 or more hours, your insulin levels are very low. Insulin is an inhibitor of lipolysis (fat burning) by blocking the metabolic process of allowing hormone-sensitive lipase to begin releasing fatty acids from triglyceride molecules. When insulin levels are low, your body is better able to release and transport fatty acids into the mitochondria to be oxidized.

In the morning, your circulating blood glucose (blood sugar) is also low. Some people might think this is a bad thing, and it can be if it ends up impairing your cardio performance. However, if it doesn’t, low blood sugar forces your body to begin using stored fats for energy because there is not enough glucose (energy to burn) to sustain your workout.

Are you still with me?

The metabolic mechanisms that enable fasted cardio to help you oxidize more fat is much more complex. In short, fasted cardio works because it helps you to become more efficient at using fat for fuel and because your hormones and metabolism are all in the perfect alignment for fatty acid mobilization.

Ideal Candidates

Fasted Cardio would be beneficial to your workout routine if you’re looking to burn body fat or tap into those stubborn body fat reserves (i.e. hips, tummy). There are situations however, where I would not recommend fasted cardio, such as if your cardio sessions are suffering because of a lack of energy or you suffer from hypoglycemia.

Are you a morning person? If so, that early morning cardio might be right for you!

Begin with 15 minutes of cardio at high intensity (I, personally, run) and follow with an additional 30-45 minutes at a moderate intensity.

2 thoughts on “The Ins & Outs of Fasted Cardio

    • Hi Amanda! 🙂

      No. In fact, your body is going to absorb & use supplements more readily in a fasted state vs. a fed state. Supplements, like preworkout, won’t put your body into a fed state.

      Your preworkout may have an extra kick taking it on an empty stomach though, but may also cause nausea (has happened to me before) just make sure you drink enough water before & during your workout to combat this.


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