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Is Fasted Cardio Good For You?

By Rachael Attard, Updated Nov 13, 2019
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.

HOW YOUR BODY USES ENERGY

Your body uses two main pathways for energy.

ANAEROBIC PATHWAY

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.

AEROBIC PATHWAY

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.

cardio

SO IS FASTED CARDIO BENEFICIAL?

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

Picture of Rachael

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.

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

    Becca says:

    I’ve started going the gym running on treadmill and stair master within 3 weeks my legs have gone huge. Thankfully I’ve found your page and I’ve been doing all the wrong exercise for my body type. So going forward just walking for me. Long walks do you recommend for slimming down big thighs?

      Ana - Lean Legs Support says:

      Hey lovely,

      Long walks are amazing for slimming down! Rachael suggests at least 10 000 steps daily for the best results! :)

      Love,
      Ana

    Natasha says:

    Hi!

    I’m in between mesomorph and endomorph. I’m trying to get walking more, but it’s hard because I have to shield someone in my home so have to wear a mask at all times which makes power-walking quite hard work. I’m currently following a Time Restricted Feeding schedule of 18:6 and generally eat my first meal of the day at 13:30 and my last at 19:00, which means I’m in a fasted state in the mornings.

    I’m at an average level of fitness and was wondering how much benefit there is to doing resistance training (bodyweight exercises) or HIIT workouts in a fasted state? Aside from energy concerns, are there any risks I should be aware of? As walking isn’t ideal, this exercise is kind of what I’m limited to at the moment.

    Also, my brother has an Air Bike (assault bike) too – is it possible to achieve my low intensity cardio needs on this (going slow-ish, rather than high intensity)?

    Thank you!
    Natasha x

      Sanja - Lean Legs Support says:

      Hi lovely,

      Thanks for reaching out! <3

      If you are a lovely mix of mesomorph/endomorph, Rachael wouldn't recommend doing HIIT because it causes you to bulk up. Walking is the absolute best way to get slim, toned legs :) I know you said that walking is not ideal at the moment, but you don't have to do all the walking at once. You can break it up throughout the day. Or if you have a treadmill, you can still get the same results! Just make sure that the incline is on zero :)

      As for intermittent fasting and resistance training, you can try it and if you feel that you’re pushing yourself too far, stop :) Rachael has an awesome blog on intermittent fasting that you can find here.

      The Air Bike will most likely cause you to bulk up. Rachael suggests that endomorphs avoid cycling completely, while some mesomorph can get away with it. But even for mesomorphs, she recommends cycling only 1-2 times per week to avoid getting bulky.

      I hope this helps, please let me know if you have any questions! xx

      Love,
      Sanja

    Yvette says:

    Hi, thank you for this great article.
    I started walking regularly and noticed that after walk I have muscles paint in the outer side of my lower leg, probably it is the peroneus longus. My lower leg shape is overall quite unusual, my inner muscle is very small, and outer is big. I can see other people have the oposit, where is the gastrocnemius is bigger and mine is almost not existing.
    Maybe I need to change my walking techniq/style to stop the muscle pain and the growth of my outer side and help the inner side growth ?
    What can I change with my style?
    Thank you,
    Yvette

      Ana - Lean Legs Support says:

      Hey lovely,

      I asked Rachael about your situation, and here is what she said:
      “I would start with shorter walks and then build up so your muscles can get used to it. So for example just start with 20 minute walks for 1 week, then increase to 25 minutes the next week, etc. Also make sure you stretch and foam roll afterwards. I would also recommend going to see a physiotherapist or doctor if you are experiencing muscle pain.”

      Wishing you all the best! xx

      Love,
      Ana

    Sally Lapkus says:

    Hello Rachael, it’s so nice to find you. You mentioned eating low carbs to get the most of the fasted cardio, but as a mesmorph you suggested 35% so does that mean we should stick with that, or go even less? Thank you :)

      Sara - Lean Legs Support says:

      Hi lovely <3,

      Sticking to your macros breakdown, according to your body type, is the way to go!:)

      Please let me know if there's anything else I can help you with!

      Love,
      Sara

    Cindy says:

    Hi Rachael, what should I do if I overate too much carbs the night before? My calories were low but carbs were too hard to minimize.. Would my fasted cardio be a waste the next morning? What can I do to make the most of it and still burn fat for case like me? Thank you for your help.

      Ana - Lean Legs Support says:

      Hey lovely <3

      It is okay, don't feel bad! One day can't ruin your whole journey. :)

      Fasted cardio would be great.
      Doing any type of recommended physical activity is better than nothing, so just continue and stay dedicated and motivated!:)

      Love,
      Ana

    Michelle says:

    Hi, would it be ok to wear 1kg wrist weights whilst brisk walking, or would this contribute to bulky thighs, as I would effectively be using my legs to move more weight.

    Thanks

      Ana - Lean Legs Support says:

      Hey lovely,

      Thanks for reaching out!

      It shouldn’t bulk you up, but that could depend on your body type, muscle memory, etc.
      If you notice it bulking your legs up then stop doing it. :)

      Love,
      Ana

    Vicky says:

    Hi Marina,
    Thank you for your feedback! So are you saying doing power walk after resistance training is MORE effective for fat loss than fasted power walk? Id rather choose one or the other. Thanks again! =)

      Ana - Lean Legs Support says:

      Both are totally effective! :)

      Feel free to try out both versions and you will see what works out for you better!

      Love,
      Ana

    Vicky says:

    Hello, i love your blog!! Thank you for sharing your knowledge :) So since carbs are used first then fat, would it be ok if I start with fasted power walk then run after? would that give me more chance to burn more fat? I know it would be tiring but I’m a beginner runner so i can only go a few mins anyway lol! Definitely hoping to be an avid runner some day.

      Marina - Lean Legs Support says:

      Hey lovely,

      If you want to speed up your fat loss process, you could try power walking after your resistance training sessions :)

      This is what Rachael usually recommends.

      Let me know if you have any other questions! xx

      Love,
      Marina

    Michelle says:

    Hi again,

    Will I plateau doing 10k walks 3-5 times a week? I can’t swim very well and I don’t like jogging, so walking works well for me. I know a plateau can happen with other workouts, but is LISS exempt from this or should I try to change it up somehow?

    Also, with regards to my full weekly workout routine, is it ok to do the exact same workout routines every week and change it up after 4-6 weeks to avoid a plateau? I see people talking about this on the internet and saying we need to change our exercises after a few weeks. I am am endomorph and I do the same glute work, cardio and Pilates routine twice a week and HIIT once a week and my upper body and stomach twice a week. I do the exact same routines for each area, twice a week, so that I can maximise the muscle growth where I want it and lose the fat and muscle from where I don’t want it. But instead of this, should I be doing two DIFFERENT stomach/legs/arms routines, etc, every week, instead of the exact same ones?

    Thank you

      Tijana - Lean Legs Support says:

      Hi lovely <3

      As with any exercises, after some time, if you notice that you don't get the same results, you need to spice it up a bit - this goes both for cardio and resistance exercises. You can increase the number of steps (or the time you spend walking), increase the number of repetitions or change your regime - the choice is yours (and your body's, of course) :)

      The only thing that Rachael doesn't recommend for endomorphs is HIIT - I would avoid it entirely if I were you. You can read more about recommendations for endomorphs here.

      I hope this helps! xx

      Love,
      Tina

    Michelle says:

    Hi Rachael,

    So glad to have finally found someone who speaks for endomorphs.

    I have started walking as my LISS, but I’m concerned about shin splints. I keep getting the pain and obviously I can’t walk when the pain is still there. Will I stop getting shin splints the more my body gets used to walking? Online it says you have to strengthen calf muscles to combat shin splints, but I was born with big calves and thighs, so I’m weary of doing that in case my calves get any bigger. Having said that, if that’s what I need to do, is there any particular exercise/stretch you can recommend that will help prevent shin splints. Obviously the least bulking, the better, especially due to the fact that I have cankles as well as big calves. 😩

    Thank you.

      Ana - Lean Legs Support says:

      Hi lovely,

      Sometimes repeating the same muscle movements over and over can cause problems like shin splints or tendinitis.
      Try walking slower if you are doing it aggressively, stretch well and have rest days!

      Your legs should get used to walking pretty soon, but if your pain is unbearable visit your doctor or specialist, just in case. :)

      Hope I helped! xx

      Love,
      Ana