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!  🙂



  1. 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.
  2. 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.
  3. Wallis.G., Gonzalez2.J.: Is exercise best served on an empty stomach? Proceedings of the Nutrition Society 2019 : 78, 110–117
  4. 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.

Anna Lewandowska

Athlete and nutrition specialist. Multiple medalist of the national in traditional karate in European and World Championships. Author of workout plans and books on healthy lifestyle that have helped her motivate over a million of people to change their lives for the better.

Founder of Healthy Plan by Ann, Diet & Training by Ann. CEO of Foods by Ann. Co-founder of Baby by Ann.

Wife of footballer Robert Lewandowski, the captain of the Poland national football team and Bayern Munich player. Read more »

Comments No Comments

Join the discussion…

Comment is required

Sign is required