Does fasted morning cardio work?

Many people have never heard of the term ‘fasted cardio.’ Fasted cardio refers to working out in the early morning hours on an empty stomach. When you first wake up in the morning, your system will have usually been without food for eight hours or more. After sleeping all night, your insulin levels are low, so when you start to work out, your body will be forced to burn fat for energy.

Fasted morning cardio may not work for overweight individuals

Bodybuilders, athletes, and fitness enthusiasts often choose to perform cardio early in the morning before they have consumed any foods. The combination of working out and fasting is believed to help the body shed unwanted fat. Performing only 20 minutes of high impact aerobic exercise after an overnight fast usually burns far more fat than an hour workout session for a small percentage of specific individuals. Some exercise enthusiasts believe that the low morning glycogen levels force the body to burn stored fat. Unfortunately, researchers have found that fasted morning cardio may not cause your body to burn more fat than any other workout if you are already overweight.

Understanding the morning high-intensity workout

During the morning, a high-intensity workout might push your body too hard. To achieve the needed energy your body first pulls from its fat reserves but then starts to burn carbohydrates. If you want to use high-intensity training (HIT) to burn fat effectively, then you should not do it after a fast. HIT pushes your body to not only burn fat during the workout but also afterward because it accelerates your metabolism. The harder the exercise, the longer your body will burn fat. Of course, to indeed undergo a HIT session you need fuel, so that makes working out after a morning fast tricky.

HIT burns more calories

In the early morning hours, your energy level is at an all-day low which makes it difficult, if not impossible, to achieve any significant HIT workout truly. Undoubtedly, your performance will be significantly impaired, and your workout made ineffective. According to Brad Schoenfeld, MS, CSCS at the Global Fitness Services in Scarsdale, New York a small pre-workout meal will supply enough fuel for your body to perform successful fat-burning HIT exercises. With HIT, you will burn a far greater number of unwanted calories, which only heightens weight loss.

Protein loss during morning cardio

Another factor to consider when trying to decide if you should try morning cardio after a fast is that your body will also suffer a protein loss. Performing morning cardiovascular exercises appear to adversely affect your body’s natural muscle mass, according to recent research.

HIT helps burn fat more effectively

Typically, if you have a high ratio of fat to burn such as a female with 16 percent or more body fat or a male with 8 percent body fat then fasted morning cardio rarely works well to lose fat. Instead, you need to focus more on HIT and other weight loss options to achieve your goals.

Fasted morning cardio effective for certain individuals

Most researchers agree that athletes and bodybuilders who are keeping an extremely strict dietary plan do achieve success with fasted morning cardio because they are already on a glucose-depleted plan. The training approach of such individuals has already depleted their body’s glycogen which is what the body typically uses for fuel. The lack of glucose in their system forces the body to burn fat and protein. However, these fat burning results are only obtained in individuals who are already at peak physical ratios such as bodybuilder or athletes. Overweight individuals appear to not receive help from any significant fat burning increases. Instead, people who are looking to lose fat should avoid early morning cardio after a fast and instead focus on high-intensity workout regimes to effectively lose fat and slim down.

If you opt to try fasted morning cardio, then try 15-20 minutes or less of high-intensity interval training in the early morning. You can also choose to undergo low-to-moderate intensity steady-state cardio too. However, if your goal is fat loss, then most researchers agree that it is better to avoid morning fasting followed by cardio because you will not achieve your goals as successfully as performing focused HIT during the day.


Schoenfeld, B. (2011). Does cardio after an overnight fast maximize fat loss?. Strength & Conditioning Journal33(1), 23-25.

Gillen, J. B., Percival, M. E., Ludzki, A., Tarnopolsky, M. A., & Gibala, M. J. (2013). Interval training in the fed or fasted state improves body composition and muscle oxidative capacity in overweight women. Obesity21(11), 2249-2255.

Paoli, A., Marcolin, G., Zonin, F., Neri, M., Sivieri, A., & Pacelli, Q. F. (2011). 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. International journal of sport nutrition and exercise metabolism21(1), 48-54.