One of the most popular debates in the fitness industry is whether doing your cardio in a fed or fasted state really matters.
Some swear by it. Others claim it’s the ultimate in Bro Science. We’ve got clients super lean doing it. We’ve also got clients super lean not doing it.
The answer, in a nutshell, is it doesn’t matter, physiologically.
Science has confirmed this, with a few studies now demonstrating that no metabolic magic occurs when you do your cardio fasted1.
However, the problem with studies is that it looks at the world through a straw and often forgets some of the intricacies that can make a successful body transformation.
What we’ve seen with training thousands of clients is that in some cases, fasted cardio can work really well, but not for metabolic reasons.
Here are three reasons why:
1. Shorter Eating Window
If you skip your breakfast and do your cardio first thing instead, you’ll shorten your day’s eating window.
For anyone who’s dieted hard before, having your meals closer to each other in the day can really help.
If you wake up, do your cardio and get ready, it could be two hours before you eat breakfast.
If you’re awake for 16 hours, you’ve now reduced your eating window of opportunity to 14 hours instead. This could make a big difference in the number of total calories you eat, especially if you follow the old school approach of eating every 3 hours.
Remember, calories do count!
2. Mindful Benefits
Given the busy nature of our clients’ lives, doing cardio first thing in the morning brings other benefits:
- It clears the mind before the day ahead and provides some much-needed head space at a time when no one will interrupt them.
- The physical and mental endorphin rush will help with reduce cortisol and bring a much more positive outlook on the day.
- If you do it first thing, you’ll be a lot less likely to skip it later on.
3. Improved Quality of Sleep
We all spend way too long inside and not enough time exposing ourselves to natural light and fresh air.
In fact, it’s actually been shown that the quicker you receive natural light after waking, the better you will sleep at night. This is because it helps regulate our biological clock and keeps it on track.
Anytime you do fasted cardio first thing, you’ll always come back feeling awake, refreshed and ready to start the day.
Our founder, Nick Mitchell, is a fan of fasted cardio in the right circumstances. Here’s a video on his thoughts:
Take a look at how you can take it to the next leevl with these workouts.
How Fasted Cardio Works Best
The key with cardio, when done fasted, is that it must be low-intensity work.
Heading outside and going for a fast-paced walk is a good option.
The reason low-intensity work for 30-60 minutes works great is it doesn’t increase our cortisol production. It may actually have a relaxing effect.
What you want to avoid is high-intensity work, such as sprints or weight training. Given the fact most of us are swimming in too much cortisol, very few have robust enough hormonal profiles to handle high-intensity work while fasted.
When you wake up, cortisol is at its highest. If you don’t eat, instead opting to train intensely, you’ll amplify this and risk losing muscle tissue.
If you do want to train first thing, but don’t want to eat a solid meal, aim to get some form of protein in, possibly with some fat to help stabilise blood sugar.
A solid choice would be a scoop or two of protein powder, or amino’s, with a tablespoon of nut butter or coconut oil.
By doing so, you’ll help keep cortisol patterns under control, stimulate protein synthesis and ensure performance doesn’t suffer during intense sessions.
To conclude, if your goal is to lose body fat, whether you do your cardio in a fasted or fed state doesn’t matter. What does matter is finding something you can stick to and with which you feel good. For many of our personal training clients, starting the day with a morning walk outside can be great for the benefits it brings outside of just fat loss.
- Schoenfeld B.J, A. A. (2014). Body composition changes associated with fasted versus non-fasted aerobic exercise. Journal of the International Society of Sports Nutrition.