The pros and cons of fasted cardio

Do the pros of fasted cardio outweigh the cons?

28 August 2020

3 min read

Fasted cardio sounds very fancy but some of you may already be doing this type of workout without realising it. Technically anytime you jump out of bed and head straight to your early morning workout without eating first, you are doing a fasted workout. 

Fasted cardio occurs when you workout to increase your heart rate without eating prior to your workout, usually between 8-12 hours before (post-sleep), however for some it can be as short as 3-6 hours depending on how quick your digestive system works. 

If you are going to have a go at fasted cardio for the first time, be kind to yourself and trust how your body feels. You may find you can perform low-intensity cardio for up to an hour (walk, jog or slow run). However, the body may take time to adjust to this new way of working out so do not be surprised if you do not last an hour the first few times you try this. You may even notice you feel sluggish when you start using this type of training as your body adapts to become more efficient at burning fat for fuel.  

Past the hour mark, your muscle glycogen levels (the body's energy source) will become low and you will feel like you are running out of energy. 

Then the best part about fasted cardio, eating after! Aim to eat within 45-60 minutes post-workout, consuming a combination of carbohydrates and protein to restore your muscle glycogen levels. 

The key safety rules when performing fasted cardio: Do not exceed 60 minutes and stay hydrated.

To help you decide if you should give this type of training a try, check out the pros and cons below.



Workout completed - starting your day with a workout helps overcome the ‘something has come up’ moments which can interrupt your workout plans for the day. As well as enjoying the flood of mood and brain-boosting chemicals to your body which can help increase motivation and productivity. 

Avoid an upset stomach - some people simply feel better training on an empty stomach. As training fasted can help avoid discomfort, indigestion and nausea that can sometimes happen when you train post-meal.



Decreased training intensity - for many training in a fasted state can result in a less productive training session due to the lack of food. To train optimally you will not do this on an empty stomach. 

No greater weight loss - training in a fasted state does lead to a great rate of fat burning during exercise, however, this does not translate to greater weight loss overall. 

Remember fasted cardio is not for everyone, everyone has a different body so whether you workout fasted or fed all depends on what your body prefers. If your body suffers from pre workout eating induced nausea or lethargy, train fasted. If getting out of bed early and working out helps you achieve your workout in your daily routine, train fasted.

Fasted cardio at the end of the day is a tool to utilise if it syncs well to your body's physiology. If you find your performance drops when fasted, don't worry, you can still lose just as much body fat with the bonus of not feeling hungry while you work out.