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What is the point of running on an empty stomach?

Whether you're trying to lose weight while running or just getting used to your metabolism so that your absorption is better during exercise, fasting can be a way to get your body to tap into fat deposits. Fans of the fasting race usually exercise in the morning before breakfast but it is also possible to practice it during the day after four to five hours or more without eating.

Although the idea is not new, it has recently gained new traction in the world of endurance sports. Indeed, it seems in line with the final goal of many runners: lose weight and improve their performance. However, the effectiveness of this technique depends on your training objectives as well as the methods you use: short, intense and frequent outings or longer and slower outings?

Metabolism adapts

First of all, you have to consider cardio on an empty stomach as well as the consumption of fat in the longer term context of your weekly caloric intake : It's not just the calories consumed during exercise that count. A great example is high intensity interval training where the runner can do 10 high intensity efforts for a short period of time, for example 20 seconds with only 30 to 60 seconds of rest between two iterations. The total amount of calories burned by this kind of workout is small, but the long term metabolic gains are real.

Race on an empty stomach: learned mix

Eating or not eating before a workout depends on exactly what type of workout you are practicing. Eating before an effort will not cancel all fat consumption by the metabolism during the race, and not eating will not lead to massive overconsumption of fat as some would like to believe. It's about training your body to be able to deal with all kinds of situations.

For a low-speed session like a one-hour race, eat less before the race by compensating for a more consistent recovery thereafter stimulates activated enzymes during fat consumption. However, eating before exercise is not totally devoid of interest either. Indeed, leaving on a full stomach or at least satisfied allows you to endure a longer session. In fact, the main thing lies in the rider's eating habits throughout the week as well as in the frequency of the sessions.


fasting race

Burn carbohydrates or fats?

Most runners eat carbohydrates before the race so as not to run out of energy: a plate of pasta the day before the marathon for example. When practicing cardio on an empty stomach, the focus is on the body's ability to consume fat. On an empty stomach, during the least demanding parts of the race, the runner consumes his fats and preserves its carbohydrate reserves for the most complicated segments.

A well-trained runner is able to burn fat as well as carbohydrates. This allows him to have a greater reserve of energy at his disposal. Both sources are not not interchangeable. During marathons and shorter formats, carbohydrates are the main source of energy used by your body It is therefore important to train while being satiated. During the races longer, like ultra trails, the body's ability to burn fat has a significant impact.

There is a separate category, those who combine long and intense effort: runners capable of running a marathon in less than three hours. They work to consume only their carbohydrate reserves during the effort because the fat does not generate enough energy to follow their important demand. Burning fat consumes oxygen, which is usually the main limiting factor when one is fit to run a marathon in less than 2h30.

If you decide to take the plunge and exercise your body on an empty stomach, we have some final tips for you to wrap up:

  • Start gradually your fasting practice by increasing the duration step by step and staying at rather low speeds at first.
  • Do not get into a completely fasting session if it is to finish hungry and feast after the effort.
  • After a fasting race, recovery is even more important. 

To learn more about sports nutrition and understand how to set up a nutrition strategy us.

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