Is training on an empty stomach a good practice?

The idea of training on an empty stomach, especially in the morning, and performing aerobic activities, is nothing new in the world of performance. Training for a certain period, even for more than an hour, at a medium to low intensity and without having eaten at breakfast, would accustom the body to metabolizing fats efficiently which is a fundamental ability for endurance sportsmen.

Not all technicians and athletes agree with this methodology and even in the scientific literature you can find pros and cons. However, the subject has become somewhat topical recently, given that there has been a great deal of interest in what is termed "intermittent fasting".

This is a subject much investigated in the literature and the evidence supporting the effectiveness of this 'method' is comforting: it seems to be effective in weight loss and body composition modification. However, it should be considered that it is one thing to fast, even for a whole day, when the demands of the day are reduced to the common activities of the life of relationships, but it is quite another to train on an empty stomach.

How effective is fasting training?

It is not easy to give a definitive answer to the questions related to the effectiveness of fasting training because the variables to consider are considerable: time of training, type of training (aerobic or strength), duration, intensity and number of hours from the last meal.
But let's clear the field for misunderstandings: to sustain physical efforts you need energy, energy that comes from food, and the longer the duration of training, the greater the amount of energy you need. Similarly, the greater the intensity of the effort, the more fuel is needed that consists of sugars.

If one has to sustain a prolonged effort of a certain intensity, it is not possible to do so on an empty stomach, it would lead to a dramatic drop in performance and even to certain risks. For example, no cyclist, whether professional or amateur, would ever dream of starting at 200 km fast race; the same applies to a marathon runner. So, when does it make sense to train on an empty stomach? There are essentially two conditions:

• A precise training program that means inserting specific fasting workouts (generally at medium low intensity) in a certain period of time with the aim of forcing the body to use lipid stocks in a very efficient way;
• Aerobic activity of medium to low intensity (like jogging) is performed in the morning and done without first taking anything. At the end of the activity you can have a nutritional breakfast.

In the first case it is necessary to be followed by a specialized technician or a doctor, in the second it is essential to test your body and study its reactions, proceeding gradually, starting for example with 20 minutes of light running, we advise against exceeding the hour of fasting activity. If, on the other hand, you perform "mixed" activities that involve a combination of aerobic activity and strength, especially when performed at medium to high intensities, as in the case of interval training, you need to be very careful. The risks of performance impairment and, in the worst case, of hypoglycemic episodes, become significant.

Fasting for slimming?

On the other hand, the question of whether more fat would be burned on an empty stomach, which would be the ideal training method for those who have to lose weight, the scientific literature shows both favourable and unfavourable opinions, simply because the studies are generally carried out on small samples and are very different from each other, it is therefore difficult to draw conclusive conclusions from them. It is good to recommend caution, remembering that the "man car" to move needs energy. In any case, it should be noted that the physical exercise that really works is what is done regularly and consistently over the years.