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Wellness Club

Fasted Cardio- How Does it Work and Is it Right for you?


By: Kirsty Godso


You’ve definitely heard of it, maybe you’ve tried it, but you may not know exactly why and how it works. So what’s all the fuss with fasted cardio? Scientific literature specifies that the body needs a 10 to 14 hour period of not eating to be truly fasted so for almost all of us, fasted cardio would occur first thing in the morning.

How does it work?

When your body is in a fasted state, your glycogen stores are slightly depleted, and your body looks for alternative fuel sources as energy- this is when your body turns to fat as a fuel source. Studies show that fat utilization during exercise peaks during a fasted state. Exercise before nutrient ingestion promotes an increased reliance on the oxidation of fat during exercise. It also promotes sustained utilization of fat for energy post workout. The total amount of calories burnt can look the same when comparing fasted or fed cardio, but the type of energy burned is different - fat vs carbohydrates.

But how do you know if fasted cardio is both right and safe for you? This is when you need to check in with what your baseline starting conditions and goals are. You may want to try fasted cardio if any of the below apply to you:

⁃You’re healthy and looking to optimize your lifespan

-Performance: optimizing for power sports or endurance athletes

-Metabolically impaired (most people fit into this category due to the classic American diet)

From here, you can judge what your personal relationship with fasted cardio could or should be. Most of us will fall into a category where we are looking to optimize our metabolic performance, so adding in some fasted cardio in the morning can be a great way to set your body up with an effective start to the day. 

But be sure to practice it with caution. Think about what type of exercise you’re doing that day and if it’s the best choice. For example; any time you do a High Intensity workout, (this can be running such as intervals, Fartleks, speed work etc.) not fueling before your workout can shortchange both your energy and your ability to perform. HIIT workouts burn a high percentage of carbs no matter what and you will likely find that you fatigue much faster in this type of exercise when trying to do it fasted. HIIT also helps you burn fat for hours after your workout regardless of fasting. You can try fueling your body with a smaller intake of fuel such as half a scoop of protein powder mixed with water or half a banana pre HIIT if you want to be relatively fasted or, try leaving 1-2 hours after eating before working out.


If your focus is building strength, power or endurance, you’ll want to think more specifically about whether or not fasted cardio is appropriate for you. Your body doesn’t automatically burn fat instead of glucose in a fasted state; it may turn to protein instead which can cause an increase in muscle breakdown when we exercise fasted, meaning it could actually decrease our strength. Runners for example, rely heavily on carbohydrates to fuel long distance runs and can hinder their performance dramatically if they don’t have carbs to pull from. 


If you’re currently intermittent fasting and are a fitness enthusiast who isn’t training for something specific, fasted cardio in the morning that is under 60 minutes can help you optimize fat burn and can be a good addition to your routine. 

But just because fasted cardio will help you burn more fat, doesn’t mean you can eat whatever you want. To see results, you need to also be making good choices with your diet. Like everything, it’s not a one-size fits all scenario, so try it out and check in with your body. You might experience improvements in metabolic body markers but performance improvements may only vary slightly. As always, be kind to your body!