A lot of people these days are starting to do their workout on an empty stomach. Some do it on purpose, while others lack time to get a quick breakfast.
This topic has become another obsession in the sports nutrition world and a widely debated topic. Today’s article is not intended to be an exhaustive guide to opinions on the subject, nor can it replace the advice of nutritionists, doctors, and sports medicine specialists.
It is merely an attempt to offer a few hints based on information and consensus opinions on whether or not you should do your workout on an empty stomach provided by experts in the field.
First of all: Do you suffer from type 1 or type 2 diabetes, hypertension, or kidney problems? If so, this article is not for you. Eat normally, don’t train on an empty stomach, and always practice sports under the supervision of your doctor.
If you don’t suffer from these pathologies and are an amateur athlete, experts generally advise against this type of training aimed at elite athletes.
Even so, if you want to try it, do it with caution, at moderate intensity, and always listening to your body. It is also advisable to consult a nutritionist.
So what exactly happens if I do my workout on an empty stomach?
Training on an empty stomach is intended to force the body to use fats as a source of energy. During sleep, glycogen stores are depleted.
Starting from low glycogen levels will cause the body to draw on other sources of energy during training.
This energy is the fat that accumulates in adipose tissues and of which there are more than sufficient reserves.
A study published in the British Journal of Nutrition found that men who exercised at moderate intensity skipping breakfast burned 20% more fat than those who ate breakfast.
What are the effects?
This is where the nuances come into play. The answer is: “it depends.” It depends, first of all, on the type of training.
At moderate intensity, it has the effect of burning more fat. This effect will be especially pronounced in endurance training and low-medium intensity training: for instance, prolonged moderate efforts.
The reason is that carbohydrates (blood glucose, muscle, and liver glycogen) are mainly used at the beginning of the race or workout, usually in the first phase of training, when the exercise intensity is highest.
Fats are used 20 to 30 minutes after you start training
Fats start to be used 20 to 30 minutes after the activity and at moderate-low running intensities.
Pablo Sinclair, P.E. Professor at the European University, explains in a private research report that “empty stomach exercise stimulates lipolysis (lipids are used for energy production) and the oxidation of peripheral fats.”
The body can become accustomed to burning fat
There is an additional long-term effect: if the glycogen level is low, the cells will become accustomed to burning more fat.
In other words, “metabolic” efficiency is improved, according to this other study led by K. Van Proyen and published in the Journal of Applied Physiology.
The study compared two groups of individuals performing light training: one group did their workout on an empty stomach and the other trained after eating a carbohydrate-rich breakfast.
After six weeks, there were differences at the muscular level, so that those who trained on an empty stomach had improved fat metabolism, using 21% more fat as fuel than those who trained after having eaten.
Thus, training on an empty stomach can improve long runs because the intensity is lower, and endurance takes precedence over speed.
Endurance vs speed
The participants spent several hours running with a relatively low heart rate, so an improvement in the utilization of the fat reservoir as a source of energy improved their performance.
Thus, specialists agree that empty stomach training can be useful for endurance athletes where fats are used as the main source of energy.
However, if you apply high-intensity training, the result changes completely.
At high intensity, fasting under the parameters we have outlined in the first paragraphs loses its usefulness. It has the effect of decreasing performance and activating glycogenesis, which breaks down muscle proteins.
Thus, muscle mass is lost, and, what is worse, the body will not function properly, resulting in dizziness, fatigue, or hypoglycemia.
One last clarification: it seems clear that training on an empty stomach does not necessarily lead to weight loss.
As stated by physiology, sports nutrition, and personal training experts, the key to losing weight is to expend more calories than you take in.
So if this is true, it doesn’t matter if you exercise on an empty stomach or not. What’s more, if you eat breakfast, your workouts can be more intense and burn more calories.
What about muscle?
While some experts say that doing your workout on an empty stomach can help tone muscles, others say that proteins are another element from which the body can obtain energy.
For this reason, sometimes it is not only fat that is used, but also protein. When the body uses protein as fuel, muscle growth can be affected.
You may want to read: What are Muscle Activation Techniques (MAT) Used For?
In fact, people who have difficulty gaining muscle or who want to increase their muscle mass may encounter a problem if they do sports on an empty stomach. Therefore, it is not advisable to overdo it.
Fasting diets, dizziness, and poor performance
One of the consequences of doing sports on an empty stomach can be dizziness and poor performance, which will prevent the loss of calories we were talking about initially.
So, what is recommended? Practice sports on an empty stomach only on days when doing moderate cardio (never when doing weight training exercises) or having a light breakfast before practicing sports.
For all these reasons, training on an empty stomach can be convenient as long as this is done from time to time.
If sports are done daily on an empty stomach, muscle mass gain could be affected, increasing flaccidity and reducing sports performance.
However, as we said at the beginning of this post, it is still impossible to clearly answer whether it is better to do sports on an empty stomach or not because, as we have seen, there are points in favor and against it.
Workout on an empty stomach: Conclusion
Fasting training optimizes the utilization of fats as fuel and may be useful for long endurance athletes participating, for example, in ultra-distance events.
However, it has not been proven to help you lose weight or to help you slim down, and it is certainly not suitable for beginners or untrained runners.
If you still decide to train first thing in the morning, it is important to introduce it progressively, replenish your reserves after training, get a sports beverage or something to drink if necessary, and do it only in low-intensity workouts so as not to exceed the aerobic threshold, around a maximum of 65% of your capacity.