Benefits of Training on an Empty Stomach

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Τraining on an empty stomach, also known as fasted cardio, is very popular. The idea of ​​training on an empty stomach, at moderate to low intensity, especially in the morning, is well-known in the world of performance. Exercising without eating helps our body get used to metabolizing fats effectively.

However, this trend contradicts the practice of consuming energy bars and hyper-caloric gels during exercise that has been instilled in us for so many years.

We are back with opposite recommendations! But, who is right?

What is the scientific evidence behind fasting training?

Are the so much talked about the benefits of fasting training real?

Lets find out.

Imagine for a moment that you are a hunter struggling to survive and that you need to focus all your strength on getting food.

When do you think it will be most important to move?

Right after eating or when hunger strikes and you have nothing to eat?

Exactly! You will only move when there is a need.

When your body feels full, it does not want to “waste” energy, it induces you to rest, and your performance decreases. This is why we get sleepy after eating.

On the other hand, when you are fasting, your body and mind understand that it is time to strive for food and performance.

👉 Therefore, the optimal body state for physical activity is fasting.

But in addition to this advantage, there are many other benefits of training on an empty stomach. Benefits that you will have both doing strength training and running on an empty stomach.

How to train on an empty stomach

How to start

The idea of ​​training on an empty stomach is very healthy

Training on an empty stomach is what we call fasting training, and it consists of training, leaving a margin of at least 3 and a half hours between your last meal and training.

Therefore, the idea is that you do your training in the mornings or the evening-night, having lunch being your last meal. The time is not as important as the fasting period.

However, training in the morning has many advantages that will add to the benefits of training on an empty stomach, such as:

  • Release of stress and tension: when training, endorphins (the happiness hormone) are released, which implies improved mood. Therefore, a greater possibility of being more productive and positive during the rest of the day.
  • More energy in your training: when you get up is, without a doubt, when you have more energy accumulated. If you train in the morning, you can put all your energy into exercise (and recover it later when you eat).

When training in the afternoon, you are tired. You don’t feel like it. This is because a large part of your energy has already been used throughout the day.


Training on an empty stomach implies not having eaten before, but you can drink plain coffee, herbal teas, or kombucha before exercising.

These drinks will provide you with energy to help you feel better during training if you start to train on an empty stomach.

It is essential that, if this is the first time you are training on an empty stomach, you do not start with a 20km run or exhaustive strength training.

Being not used to it, many people suffer dizziness or feel bad throughout the day, try first with normal training sessions or with a medium intensity to see what your feelings are like.

Finally, when you break the fast, your food must be rich in real food and balanced in macronutrients. This article will interest you if you want to know more about what to eat after training.

Benefits of fasting training

Promotes the use of fat

Delving into the effects of doing physical activity on an empty stomach, we can see that it has the following advantages:

The body begins to use body fat as its primary energy substrate to preserve glycogen stores and minimize glucose use.

This metabolic change is exciting because quantitatively, fat is, by far, the energy substrate that gives us more energy.

However, you must always consider that if your body fat percentage is low, it is not advisable to train on an empty stomach.

Build muscles

training on an empty stomach facilitates energy supply to the muscle

It helps to develop a type of muscle fiber with a lot of metabolic flexibility (type IIa fibers), that is, capable of withstanding prolonged efforts while performing explosive activities.

Facilitates energy supply to the muscle

Fasted cardio stimulates the muscle glucose receptors called glut4

By moving on an empty stomach, we stimulate the muscle glucose receptors called glut4 to mobilize to the cell membrane so that the muscle obtains this substrate as a priority activity.

All this occurs without the need for the body to release insulin. Apart from improving our performance, it is of great clinical application in people who suffer from problems of regulation of glycemia or obesity.

Reduces the feeling of tiredness

When the movement is consistent for our body (as in the past, going to find food), our brain supports the action.

Fasted cardio reduces the feeling of tiredness

The way to achieve this is from the limbic or emotional brain, producing a neurotransmitter called dopamine.

Among other functions, this neurotransmitter is associated with cognitive ability, motivation, and pleasure.

In other words, dopamine makes us more tolerant of fatigue.

Improve your metabolic health

Energy stress caused by exercise and fasting increases the expression of energy homeostasis regulatory proteins.

In this way, a cellular signal is transmitted to improve glucose uptake, increase fat oxidation, and synthesize new mitochondria (cellular structures responsible for producing body energy).

👉 These functions are essential to maintain a healthy metabolism.

Gain muscle mass on an empty stomach

If you doubt training on an empty stomach because you do strength training and your goal is to gain muscle mass or hypertrophy, let me tell you that you can achieve it without problem training on an empty stomach.

These are the reasons:

The only and most important thing for gaining muscle mass is the protein you eat, not the calories. There is a lot of scientific studies that reaches this conclusion with reviews like this or this one.

When we are fasting, we reduce our systemic inflammation levels in the body, inflammation being a state that steals much of the protein we consume.

Fasting activates the metabolism of ketones, protectors of oxidation. This means that our muscles do not degrade so quickly.

Fasting activates the metabolism of ketones, protectors of oxidation

Ketones also increase leucine levels in the blood, and leucine is an essential amino acid for gaining muscle mass.

👉 Therefore, if you follow proper training and combine it with fasting, you can significantly improve your muscle gain level.

If you want to know more about gaining muscle mass, you can look at this article.

Fasted aerobic exercise

There is a way of education where fasting will enhance the benefits and results. Without a doubt, the best aerobic training, such as running or cycling, should be done on an empty stomach. The main reason is that this type of training is based on fat as the primary substrate.

To achieve this, we need:

The proper metabolic and hormonal context: When we eat food before training, insulin release means that we cannot use fat as an energy substrate. We have to use glucose, which is an obstacle in terms of health and performance.

Therefore, if we eat before training, we lose the primary energy source for this training type.

Oxygen: As the name itself indicates, this type of training requires oxygen (aerobic).

To use fat for fuel, we need oxygen. However, with ingestion, a lot of blood is directed to digestion and not to the muscles.

In this way, we will have less oxygen available for physical activity.

Another great benefit of fasting training is developing a type of muscle fiber with a high mitochondrial density.

But why should my mitochondria matter to me? These are cellular organelles responsible for producing the energy we need.

Besides, they are associated with better stress tolerance, healthier aging, and a better mood.


training on an empty stomach Improves metabolic health

Following lifestyles that offer physiological consistency to our physical activity gives us many benefits, and training on an empty stomach is one of them.

While the benefits of training on an empty stomach are many, it’s important to remember that not everyone feels good at first. Start with medium or low-intensity workouts when you start to train on an empty stomach to gradually discover new sensations.

Fasted training is valid for cardiovascular training and strength training, as long as it is done correctly.

The food you eat after fasting is essential to regain energy and achieve your goals.

At Gearuptofit.com, you can find many articles focused on gaining muscles and where they combine training and nutrition to achieve your goals in an easy and fun way.