To lose weight, it is essential to be in a calorie deficit situation. Practicing regular physical activity and adopting a varied and balanced diet also helps speed up the process. However, some people want to accelerate their weight loss even more and decide to train on an empty stomach to burn fat more easily. So, does training on an empty stomach really help you burn more calories and therefore fat? Info or intox ?
Reminder.
Please note, training on an empty stomach is not trivial and must be done with caution.
What are the different energy reserves in your body?
When you play sports, your muscles need energy. To obtain it, your body has 4 energy reserves. Each of these reserves will be used at different times during your physical activity but also depending on the intensity of your effort and the time of your training.
1. The creatine phosphate reserve.
Creatine phosphate is the energy element obtained by the synthesis of carbohydrate, lipid and protein reserves. A low reserve of creatine phosphate is stored in your muscles. This molecule can be instantly used to ensure muscle contraction and therefore ensure effort. However, these reserves are tiny and only allow for an effort lasting a few seconds such as a sprint (100 to 200 m) or a series of 10-15 repetitions of a bodybuilding exercise. To ensure a longer effort, you need to take a break to replenish these reserves. If the exercise continues despite everything, it is the carbohydrate reserves which will be mobilized.
2. The carbohydrate reserve.
The carbohydrates you consume will either be directly used to provide energy to your organs, or stored in the liver in the form of glycogen (100g) and in the muscles (350 to 400g). After a few seconds of effort, it is these reserves that your body will mobilize to provide energy to your muscles. This process is called glycolysis. If the effort is intense, breathing will not provide enough oxygen to your muscles. Glycolysis will then be anaerobic (without oxygen). This reaction leads to the production of lactic acid, responsible for cramps and muscle burning sensations. For endurance sports (running, swimming, cycling, etc.), breathing helps bring enough oxygen to your muscles. Aerobic glycolysis (with oxygen) is then possible and energy production can take place until carbohydrate reserves are exhausted (approximately 1 hour to 1 hour 30 minutes in the event of no food intake).
3. Lipid reserve.
Lipids are also an important source of energy for your body but unlike carbohydrates, the transformation time into energy is a little longer. As a result, the lipid reserve will be mobilized during an effort lasting more than 20 minutes (cycling, trail running, marathon, hiking, etc.) and will take over or accompany glycolysis (depending on the state of glycogen reserves). This use of lipid reserves is called fatty acid oxidation and requires sufficient oxygen supply. It is therefore mainly used in endurance sports.
4. Protein reserve.
Proteins are the last energy elements that your body will use as an energy source. It is also absolutely not recommended to draw energy from protein reserves because this leads to a loss of muscle mass. Although proteins are used mainly after the exhaustion of the other two reserves, in reality, the latter will be used throughout the effort. For this reason, it is important to include a source of protein in addition to carbohydrates in your post-exercise snack to optimize recovery.
Summary.
Initially, your body will draw its energy from circulating, hepatic and muscular carbohydrates after rapid exhaustion of creatine phosphate reserves. Then the body will transform the circulating lipids and those contained in body fat into energy. Finally, protein reserves will be used if necessary.
What are the benefits of training on an empty stomach?
After a good night's sleep, your glycogen reserve is almost, if not completely, empty. Therefore, when you train on an empty stomach, your body will have no energy reserves other than the fatty acids contained in your body fat. Such a practice therefore allows you to reduce your fat reserves more quickly. For anyone looking to lose weight, it can actually be beneficial to work out on an empty stomach to burn fat more effectively. Wanting to train on an empty stomach is also a question of digestive comfort. In fact, some people take longer to digest or eat a meal too soon before their physical activity. This can lead to a feeling of heavy stomach or bloating during exercise.
What are the risks of training on an empty stomach?
Training on an empty stomach, however, is not a practice to be taken lightly. When training on an empty stomach, it is important that your effort is short to medium duration and low to moderate intensity. These parameters ensure that you do not draw on your protein reserves and do not feel bad. Indeed, too long and intense effort on an empty stomach can be dangerous and cause nausea, vomiting, dizziness often linked to hypoglycemia and therefore the risk of injury. Studies have shown that when you exercise in an empty stomach for more than 30 minutes, you significantly increase your chances of muscle wasting and blood acidification. An increase in recovery time is also noted. Your performance will systematically decrease if your fasting effort is too intense. So although beneficial for tapping into your body fat reserves, there is no point in considering an increase in your physical performance during this type of training.
In summary.
Here are the things to put in place when you want to train safely on an empty stomach:
- Fasted training maximum 2x / week
- 30 to 45 minutes maximum
- Consumption of a carbohydrate source at the meal preceding a morning session
- If the objective is not to lose fat mass, hydrate yourself using a BEAG (exercise drinks with carbohydrate intake) to avoid hypoglycemia
- Increase your protein intake at the meal following the session on an empty stomach to optimize your recovery.
