Is Fasted Cardio Good For You?

is fasted cardio good for you?

Fasted cardio is cardio that is done first thing in the morning on an empty stomach. So is this good for you or not? I will explain, but first we need to cover a few technical details.


Your body uses two main pathways for energy.


One is known as the anaerobic pathway, and your body uses this for high intensity exercise such as HIIT, weights and short interval training. The main fuel for this type of exercise is glycogen (which comes from carbs) and creatine phosphate.


The other pathway is known as the aerobic pathway, and your body uses this for low to moderate intensity exercise such as power walking. The main fuel for this type of exercise is glycogen and fat.

When you start any type of exercise, you will be in this aerobic / fat burning zone. As your exercise intensity increases, you will switch over to the anaerobic pathway at a certain point. The fitter you are, the longer you can stay in this fat burning zone.

When you do cardio at a low to moderate intensity, the body’s preferred fuel is glycogen (carbohydrate) first, and then fats. However, the longer you exercise, the more fat your body will burn.



So to finally answer the question – it IS beneficial to do fasted cardio. This is because you have not eaten anything for a fairly long period of time, so there is not much glycogen (carbs) stored in your body, and as a result, you will end up burning more fat. Fasted cardio works better if you haven’t had a lot of carbs to eat for dinner.

It is best to do low to moderate intensity cardio in the morning. If you tried to high intensity exercise, your body would not have as much energy for it. Therefore you would not be able to do as well during your workout. If you are fit, you would likely still burn more fat doing higher intensity fasted cardio, but it is generally not recommended.

Long, slow cardio is not the most effective way of losing weight. However it IS beneficial to lean out your legs. You will not gain muscle doing this type of exercise, but you won’t necessarily lose muscle either. Read more about how to use fasted cardio to lean out your legs here.

Find out more about my workout and nutrition program that is tailored to slim down and tone your legs here xx

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Rachael is an Australian born certified personal trainer and nutritionist who holds a Bachelor degree in Science.

After struggling for years to find an exercise and diet program that is tailored to women striving for lean and toned body with no bulk she designed her Lean Legs Program. This program is tailored to each body type and focused on helping women get toned but feminine bodies, without getting bulky.

Her mission is to empower women and help them stay in shape in a healthy and balanced way.

17 comments on “Is Fasted Cardio Good For You?”

    elize says:

    Hi Rachael
    I run at least 6 days a week at a medium/moderate pace for 60 -70 minutes a day, as soon as i get up, or as early as i can before eating anything and I can say this really works for me. The last couple of months i have at least one cup of coffee with a teaspoon cremora (sometimes) and a bit of unsweetend almond milk inside before a start running, is that fine or is this consider as eating?

    I’m struggling the past 3 months slimming down my muscular thighs, I’m 44 and its not that easy as in the past or Im doing something wrong. I also have muscular thighs.
    I’m not overweight or too short (167cm), and I’m also trying to cut on carbs as much as I can, is there any other exercises i can do help slimming down my legs? Someone told me to do Ballerina Squats, don’t know if this is the right thing to do…

      Diana - Lean Legs Support says:

      Hi lovely,
      Having just a coffee doesn’t count as having eaten, but it does if you put milk or cream into it. Doing quad building exercises such as squats, lunges and deadlifts won’t help you slim down your legs.

      We would love to help you as much as we can :) so that’s why we have created the Lean Legs Program!
      Our Lean Legs Program has been designed to include the perfect type of resistance training and cardio to give you a lean and toned look, without making you bulky.
      It’s an 8 week workout and nutrition plan that will help you slim down your legs, but will also help you slim and tone your upper body and core too (the workouts are full body).
      It also includes a full meal plan, a separate recipe ebook and demonstration videos.

      If this is what you’re looking for, I would definitely recommend giving our program a go. You can find out more about it here:

      Lean Legs Program


    Phoi Phung says:

    Hi Rachael,

    Is it ok if I eat something before going for a walk since I always feel hungry in the morning?

      Diana - Lean Legs Support says:

      Hi lovely,
      If you can’t stand doing fasted cardio, of course you can go for a walk after breakfast or later. :) All the best! xx


    Elaine says:

    Hi Rachel, I think low to moderate intensity cardio is doable on empty stomach before breakfast. But my concern is since cortisol levels are high in the morning, does exercise while you’re in a fasted state interfere with the cortisol level? Won’t the cortisol level be higher? Especially for someone with hormone imbalance and high stress levels

      Rachael Attard says:

      Hi lovely, if you have high stress and already issues with your cortisol, it’s best to eat something as soon as you wake up or within 30 minutes. I wouldn’t exercise on an empty stomach. And I would also avoid doing any workouts after about 5pm so that it doesn’t interfere with your cortisol and sleep xx

    Meiga says:

    Hi Rachel,

    I am a mesomorph, and have muscular calves. Do you have any tips for making leaner calves?

    Ammie says:

    Hey Rachel,
    Actually I have muscular thighs and I wanna slim those…can u plz tell me the fastest way for this plzz I need it urgently..

      Rachael Attard says:

      Hi Ammie, unfortunately slimming muscular thighs actually takes quite a bit of time. Please have a read of this blog post on how to slim muscular thighs xx

    Bree says:

    Hey Rachael!
    I have quite muscular legs, so I’ve been looking into fasted cardio as a way to reduce my muscle. Do you have to run right when you wake up, or can you wait like an hour (and not eat during that time?) Also, do you have any more tips for losing muscle?

      Rachael Attard says:

      Hi lovely, no you can wait an hour if that suits you better. Also have a read of this blog post on how to slim muscular thighs :) xx

    Kelly Renzulli says:

    Hi Rachael!
    I’ve followed you now for so long, I feel like I know you so well! I have a question… a silly one at that (im probably overthinking) but I always try to do my cardio fasted but I was wondering if taking supplements before technically mean I’ve eaten. I take flaxseed oil, a multi mineral, a multi cut and a probiotic. Would this make any difference? The last couple of months I’ve stopped seeing and progress so I’m really trying to clean up my diet, exercise properly and get everything on point as I’m moving to Australia in July. Eeeek.

      Rachael Attard says:

      Hi Kelly, aww that is so sweet! No I would not consider that as eating, so don’t stress about that. It is quite normal to plateau. The best thing to do would be to mix up your workouts and also add in some higher calorie days into your diet. Constant dieting reduces your metabolism so this will help prevent this. Good luck with the move to Australia! You will love it :) xxx

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