As has been observed in numerous studies, temporary caloric restriction helps reduce risk factors for various diseases, including metabolic syndrome, cardiovascular disease, cancer, and even neurodegenerative diseases.
For these reasons, and because of the fat loss that is often expected, many people consider trying intermittent fasting. whether it’s bringing dinner earlier, delaying breakfast, or manipulating meals throughout the day in such a way that there is a period in which we do not eat food for at least 12 hours.
However, it should be noted that many of the effects associated with fasting do not come from the hand of fasting, but rather from the caloric deficit that usually accompanies it, that is, we improve our health because we are in a caloric deficit and thereby lose fat. Although there may be mechanisms that associate fasting with greater youth and life expectancy, most of the beneficial effects depend on the induced caloric deficit.
Having said all this, what place does training occupy if we want to do it on an empty stomach? In this article We explain the pros and cons that exist when doing strength or cardiovascular training on an empty stomach.
What are the pros and cons of doing strength training on a fasted state?
The pros
People who do strength training tend to seek to gain strength, muscle mass, or both. By definition, with strength training you will gain strength, but what happens if you decide to train on an empty stomach? Waking up in the morning and going to work out without having breakfast would be enough to consider this as a fasting workout.
But we must not confuse training in a fasted state with training completely depleted of glycogen, that is, empty.
If you just skip breakfast and go to the gym to train, your muscle and liver glycogen levels will be practically intact because the meals you had the day before matter. No one runs out of glycogen or lowers blood sugar from skipping breakfast.
This is important to say because in a context like the one we describe, performance would not be affected. In fact, many people report feeling lighter during training and more focused. This can be explained by the increase in orexins, hormones with a stimulating effect closely related to the state of wakefulness and with food intake.
The cons
If our goal is to gain muscle mass, training on an empty stomach is not contraindicated per se, but it is true that with this goal you must eat a lot of calories, that is, you must be in caloric surplus.
Especially active people can have problems to ingest all the necessary calories during the day, if they even skip breakfast they will have to allocate more calories to a smaller feeding window with the disorder that it supposes.
In this scenario, training on an empty stomach can be a trip to yourself, not because you will gain less muscle but because it will be more difficult for you to manage the rest of your meals.
What are the pros and cons of doing fasted cardio training?
The pros
In the first place, we could highlight the lightness that is experienced when running on an empty stomach, as in the previous case. If we are going to train for less than 60-90 minutes, performance will not be affected as long as we are well hydrated.
If we talk about fasting cardiovascular training to increase fat loss, we must say that for the general population, it does not work.
We have a 2014 study carried out by researchers and disseminators Brad Schoenfeld, Alan Aragon and James Krieger among others. It is the first study that investigated the effects on body composition of cardiovascular exercises in a fasted state during a context of caloric deficit.
The results do not match what popular belief dictates: no significant differences were found in body composition between the group that performed fasting cardio and the group that performed it fed.
However, in people with low fat percentages (less than 15% in men and 22% in women), the mobilization of fat from adipose tissue is the main problem when it comes to losing fat since the areas where fat accumulates little remaining fat are areas with poor blood supply, which hinders the access of catecholamines and subsequent transport of fatty acids. In these cases, the simple deficit is usually not enough to mobilize the adipose tissue in these areas, so it is necessary to follow stricter and more specific protocols such as the fasting cardio itself, intermittent fasting or specific supplementation. In these cases, fasting cardio is helpful.
The cons
If we are talking about a standard resistance training of short or medium duration, say less than 90 minutes, in principle we should not have anything to fear, although It will depend on the previous nutritional status of the individual, the modality practiced and the intensity of the training.
Now, if we intend to perform over long distances, beyond 90 minutes or 20 kilometers, to put a reference, fasting training is not the most appropriate. You may be able to start fasting but you will be obliged at least during exercise to take some kind of gel or sugary drinkotherwise you are likely to experience hypoglycemia at some point.
In Vitónica | More fat on your plates does not mean more fat on your body: how a high-fat diet does not have to make you fatter
In Vitónica | Cardio, before or after strength training? It depends on your goal in the gym
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