The Pros and Cons of Working Out on an Empty Stomach
Training on an empty stomach, especially for weight loss, has become quite common and even trendy. However, such workouts are controversial and raise some questions. What is it really like? I’ll try to show you some advantages and drawbacks of such training.
Where does energy come from?
Let’s start with the fact that our body obtains energy from food, and more precisely from energy substrates. There are four basic substrates: carbohydrates, fats, protein and alcohol. Our body needs energy in the form of a chemical compound – ATP (adenosine triphosphate) to work properly. ATP is formed as a result of the transformation of energy substrates and is a source of energy. This process occurs in cellular mitochondria and is not always the same. Everything will depend mainly on our physical activity, its duration and intensity of the effort.
Your training goal is key
In the morning, after waking up, insulin level is the lowest and glucose level is the highest, which causes a greater transport of fat to the muscles, where they are burned. You should remember that on an empty stomach you do not work with strength and endurance to the same extent as you would after an energy-boosting meal. So the conclusion is: what is your training goal? Do you want to burn fat or be stronger and build muscle mass? If you have already set your goal, we can now proceed to the pros and cons of this workout.
The pros of working out on an empty stomach:
- it reduces body fat and body weight effectively,
- you feel light during the training,
- workout performed in the morning is like a strong coffee and gives you an energy boost for the whole day,
- better regeneration after a carbohydrate meal,
- short and less intense.
The cons of working out on an empty stomach:
- discomfort, lack of energy if the training is too long (over an hour),
- lower maximum oxygen uptake (VO2 max) during exercise, i.e. decreased endurance,
- it won’t work if you choose a high intensity workout, e.g. HIIT,
- workout on an empty stomach requires training experience.
To sum up, working out on an empty stomach is especially recommended for those on a weight loss diet, when you focus especially on losing fat. People who prefer shorter and less intense strain can easily try such workouts. It definitely won’t work if your goal is to build strength and endurance. The choice is yours, but remember to eat a wholesome meal after your training! 🙂
How to try it without ruining the session
Everything above adds up to a fairly narrow set of conditions, and they are worth stating as rules rather than leaving scattered through the lists. Keep it under an hour, because past that the lack of energy is what you will remember from the session. Keep the intensity low: this is the wrong morning for intervals, for a heavy lift or for anything you would describe as a hard session. Drink through it, since a night’s sleep costs you fluid as well as fuel. And treat the meal afterwards as part of the workout rather than as a reward, because that is where the carbohydrates you did not have beforehand go.
If you have never trained fasted, do not make your first attempt a long run. Ten or twenty easy minutes tells you what you need to know: some people barely notice, others feel it within the first five. That difference between people is the reason the post says the method requires experience, and there is no way to find out which group you are in other than trying it briefly.
When to ask someone first
Fasted training is a scheduling choice for a healthy adult, not a method with a universal green light. If you take medication with meals, if you are pregnant or breastfeeding, if you have diabetes or any condition where a long gap without food matters, the timing is a question for a doctor rather than something to try out on a Sunday morning. The same list appears in the post on losing body fat, where the eating window rather than the training is what shifts.
What you eat before training on the mornings you do eat is a separate subject, covered in what to eat before your run. And if you would rather not decide any of this session by session, the Diet & Training by Ann app plans the training and the meals around it together, so the order of the two is already settled when you wake up.
Frequently asked questions
Under an hour. Past that the discomfort and the lack of energy are what you will remember from the session, and this post lists exactly that as the first drawback of training before breakfast.
High intensity work, intervals such as HIIT, and anything you would call a hard session. Endurance is measurably lower before breakfast, since maximum oxygen uptake drops, so a fasted morning is the wrong slot for a session that depends on it.
Yes, and it is worth treating the meal as part of the session rather than as a reward. A wholesome meal with carbohydrates afterwards is where the fuel you skipped beforehand goes.
This post says it requires training experience, and the sensible way to find out how you react is ten or twenty easy minutes rather than a long run. Some people barely notice the difference and others feel it within the first five minutes.
Anyone who takes medication with meals, anyone pregnant or breastfeeding, and anyone with diabetes or another condition where a long gap without food matters. For them the timing is a medical question rather than a scheduling preference. If you would rather not settle the order of training and meals session by session, the Diet & Training by Ann app plans the two together.
Bibliography
- RehrerNJ1., Beckers.E., Brouns.F., Hoor ten. F., Saris.WH.: Exercise and training effects on gastric emptying of carbohydrate beverages. Med Sci Sports Exerc. 1989 Oct;21(5):540-9.
- Paoli.A1., Marcolin.G., Zonin.F., Neri.M., Sivieri.A., Pacelli.QF.: Exercising fasting or fed to enhance fat loss? Influence of food intake on respiratory ratio and excess postexercise oxygen consumption after a bout of endurance training. Int J Sport Nutr Exerc Metab. 2011 Feb;21(1):48-54.
- Wallis.G., Gonzalez2.J.: Is exercise best served on an empty stomach? Proceedings of the Nutrition Society 2019 : 78, 110–117
- Woon Kim.T., Hoon Lee.S., Hwan Choi.K., Hyun Kim.D. Tae Kyung Han.T.: Comparison of the effects of acute exercise after overnight fasting and breakfast on energy substrate and hormone levels in obese men. J Phys Ther Sci. 2015 Jun; 27(6): 1929–1932.
Comments No Comments
Join the discussion…