Why Fasted Cardio Works So Well for Burning Body Fat


One of the biggest reasons most people buy a gym membership or start assembling a home gym is to lose weight. The pursuit of weight loss is nothing new, and it will be something at the forefront of people’s minds for many years to come. Health concerns, difficulty of daily life and simply wanting to look more fit are all huge motivators to lose weight, and there are a million theories on how to get that done quickly and efficiently.

Most diet and weight loss fads come and go due to their ineffectiveness, but some stick around and stay mostly out of the spotlight due to lack of education or improper use. Standard cardio has been the preferred method of losing weight over many years. Running on the treadmill, cycling, rowing and the Stairmaster have all been staples of those looking to lose weight. The biggest aspect of why standard cardio fails as a super effective weight loss tool is that it simply loses effectiveness the more you do it. As your body adapts to the energy output, you’ll need to do more and more cardio to burn the same amount of calories and get the same benefit. That’s why it is time to switch up how we approach cardio.

Fasted cardio is an extremely effective method of losing weight that is starting to get more time in the spotlight due to its several benefits – mostly how quickly and efficiently it burns fat. Transitioning to regular fasted cardio can be a pretty huge lifestyle adjustment, but once you hit the groove, the benefits start showing up almost immediately in the form of reduced body fat and a leaner physique. In this article, we’re going to break down fasted cardio, look into what makes it tick and describe variations for different goals.

What is Fasted Cardio?
Fasted cardio is pretty self-defined via its name – doing cardio while in a fasted state. However, this doesn’t mean you have to stop eating for days and start doing cardio, it simply means that you do cardio in the morning while your body is in a fasted state. Breakfast is called “breakfast” because the first meal of the day breaks the fasted state entered during sleep. If you stay in this fasted state and perform cardio, it can be extraordinarily effective. However, this modality and ideology requires you to be an early riser, which can take a while to get used to. Many people prefer to workout at lunch or after work, and transitioning to fasted cardio in the morning can initially be difficult before their bodies get used to the early exercise regimen.

Fasted cardio can be performed with pretty much any cardio exercise. Intervals on a treadmill or cycle, plyometrics, rowing and boxing are all great options for performing fasted cardio. As long as you’re performing the exercise in a fasted state, you can do pretty much any modality if your goal is to lose weight. If your goal is to burn fat while preserving muscle, your options are pretty limited, as fasted cardio is so effective at burning calories that you have to choose your exercises extremely carefully – we’ll get into this a little later.

How Does Fasted Cardio Burn Fat?
Now that we’ve taken a look at what fasted cardio is and how it’s performed, exactly how is it effective at burning fat? The answer is simple enough: fasted cardio attacks fat when it has no protection. Before you break your fast and eat your first meal of the day, your insulin levels are low and your fat is in a vulnerable state before it is re-fortified with food. Leaving your body in that fasted state and performing a cardio session is effective because the fasted state puts your body in a position of energy usage, and not so much of energy preservation. This dietary ideology, along with intense cardio exercise work together to produce a method of exercise that strips away fat and leaves you shredded.

Fasted Cardio Modalities
Fasted cardio can be performed on all of the traditional cardio modalities to still get the “fasted cardio” benefits. Of course, higher intensity exercise will burn more calories and yield more weight loss. Higher intensity modalities include circuit training, Tabata-style training, interval training and a few others. These high-intensity, burst-style training methods are time efficient and have a high caloric requirement, which means that these are the methods that will help you lose weight the fastest. The modality is pretty much down to preference, and doing something you enjoy will help to ease the transition into working out in the morning before a meal, as the process of getting into that routine can be tough.

Although circuit training is definitely a possibility for fasted cardio, it isn’t recommended to do a circuit with resistance-based exercise where you’re going heavy. Due to the fasted state your body is in, your muscle glycogen stores will be low and any weighted exercise will be far more difficult and less beneficial (in the scope of building strength or muscle) than when you perform weighted exercises after a proper pre-workout meal. For fasted-cardio, stick to either strictly cardio exercises, or exercises with very little resistance performed at an intense tempo.

Fasted Cardio and Muscle Retention
Although fasted cardio is an incredible method of shedding fat, it will also eat up your muscle if you choose the wrong exercise. The thing that makes fasted cardio so effective – performing exercise while your body is in a starved, or fasted state – also leaves your muscles very vulnerable to be broken down for energy. It was long thought that fasted cardio simply could not be performed while effectively preserving muscle, until one exercise broke through and served as the gold standard for muscle-preserving fasted cardio: incline treadmill walks.

Walking has long been one of the go-to cardio exercises for bodybuilders to target body fat, as it is low intensity, low impact and puts your body in a state to burn fat instead of muscle. The purpose of the incline is to raise the intensity just a bit and make it more of a muscular challenge. This isn’t a challenging workout that will have you huffing and puffing towards the end, but it definitely works to strip off fat. Incline treadmill walking won’t be as effective at burning fat as sprints or interval rowing, but it will allow you to hang on to a whole lot more muscle.

Final Thoughts
With all of the questions and myths surrounding cardio, it’s nice to be able to lean back on this tried-and-true method of burning body fat. Whether you do high intensity exercise with the goal of quickly shedding weight or you’re implementing fasted incline treadmill walking to target body fat, while retaining lean muscle mass, fasted cardio is definitely a training style that can work for anyone. If you’re not an early riser, the transition to morning cardio workouts will take a bit of getting used to, but once it becomes routine and your body transitions to the new schedule, you’ll be on track to start burning off unwanted body fat!

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About Author

Cole Matthews

My name is Cole Matthews and I'm a certified personal trainer who's a major health and fitness geek with a huge passion for writing. See my profile page for more information!


  1. Avatar
    Nothemba Ncube on

    Thank you Cole for this inspiring article. I realized something just a day ago. I usually walk on the stairs to the fourth floor to a building and at the end of the fourth floor I will be sweating like a pig and huffing and puffing. One day when I had not had anything to eat, when I got to the fourth floor I felt great! I would love to give this a try and run in the morning. Thank you!

  2. Avatar

    What are your references? Do you have any studies that have been done on fat loss with fasted cardio versus regular cardio?

    • ShapeFit

      Hi Cindi – There is a study that was published in the British Journal of Nutrition that showed participants who did fasted cardio burned almost 20% more fat compared to those who had consumed breakfast before their workout.

    • Avatar

      Hi Cindy – The article is correct. My experience of practicing both kinds of cardio interchangeably for the last 30 years makes me an excellent evidence of this thesis. I am 63 years old, weigh 74 kgs with 9 mm of fat according to body fat calipers.

  3. Avatar

    For incline treadmill walking, how long do you have to walk and at what intensity? Are you supposed to keep your heart rate at a certain level? How many days a week do you do this? I am not trying to lose weight, just lean out.

    • ShapeFit

      Hi Bobby – For walking on a treadmill at an incline, shoot for at least 30 minutes per workout (45-60 minutes is ideal). The intensity should be high enough to break a sweat after about 10 minutes. You can use a heart rate monitor, but since everyone is different it will be difficult to determine your ideal range. It’s important to walk fast enough to burn a sufficient amount of calories during your workout. Depending on how much body fat you need to lose, start out with 3 cardio workouts per week and then increase it from there if you’re not losing the amount of fat you would like to.

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