In this article, we will look at the benefits of fasted cardio workouts and the drawbacks, to help you decide if you will get a better result if you exercise before eating breakfast.
There has been much discussion regarding whether or not there is merit to doing cardio in the morning on an empty stomach.
This is something that even fitness experts can’t agree on, with some firmly in one camp, some the other, and others sitting on the fence.
Those in favor of fasted cardio workouts are of the opinion that working out after an eight hour or longer fast burns more calories.
Naysayers argue that because glycogen stores are low after sleeping, exercising without eating first burns lean muscle rather than fat.
Then there are those in the middle who acknowledge the potential benefits of fasted cardio workouts providing precautions are taken. These people recommend having a light carb-free breakfast before working out. While anecdotal evidence supports this theory, no studies have been done to prove that this will burn more fat.
Keep reading to find out more about the potential benefits of fasted cardio workouts, and the drawbacks.
NB: It’s essential that you drink water before, during, and after your workouts.
When referencing eating before workouts, this means a few hours prior to, not immediately before exercising.
Table of Contents
Potential Benefits of Fasted Cardio Workouts
When we wake up after a full night’s sleep, our fat reserves are our main energy source until we eat. After eating, glycogen levels rise and turn into glucose, which is a primary source of energy.
Working out expends calories. Without fuel to exercise, your body will use its fat stores. If you eat before exercising, your body will burn calories from your most recent meal rather than tap into its fat stores for energy.
Additionally, our level of the hormone cortisol, which helps to turn fat into energy, is higher in the mornings.
Video discussing the pros and cons of fasted cardio workouts
Studies on the Pros and Cons of Fasted Cardio
Numerous studies have proven the benefits of fasted cardio workouts. One such study, undertaken at the University of Kansas in 1985, researched the effects of a high-fat diet and how calorie expenditure varies depending on the time of day the participants exercised.
The conclusion was that morning workouts burn more calories than an identical workout done later in the day.
A recent 6-week study conducted in Belgium supports this finding. For the duration of the research, all of the 27 adult male participants ate fat-rich, high-calorie foods.
The men were assigned to three groups. Group one refrained from exercise, while groups 2 and 3 performed identical rigorous running and cycling workouts daily.
The members of one group of exercisers trained before having breakfast, while 
the others trained after their morning meal.
By the end of the study, the sedentary men had gained weight. The participants who ate breakfast prior to exercising also put on weight, but only half as much as the non-exercisers.
The men who trained before their morning meal did not gain weight. They also had better test results than the other two groups in regards to insulin resistance.
Several other studies on the pros and cons of fasted cardio showed that people could burn as much as 20% more body fat by working out before breakfast.
However, some studies concluded that there is no significant difference between working out in the morning before eating and working out later in the day.
These studies also showed that working out before eating can decrease muscle mass. This is due to the body using proteins building blocks, amino acids, for energy, with approximately 10% more protein burned during workouts. Over time, this could result in a significant loss of muscle.
Some experts who take the middle ground in the debate recommend taking 10-20 grams of whey protein before your sessions to counteract the possibility of muscle loss. While anecdotal evidence offers this as a solution, to date, no studies have been undertaken to prove it.
Potential Drawbacks of Fasted Cardio Workouts
Those against exercising without first eating claim that not only will you not burn extra fat, but that your workout could also be less effective. This is because without fuel, you may not have enough energy to perform at your best, and if you aren’t putting in as much effort you will burn fewer calories.
Other experts acknowledge the positive findings of the studies, but say the extra calories burned are negligible.
Next, we will look at some indisputable pros and cons of fasted cardio workouts.
The Pros:
- Numerous studies have shown the benefits of fasted cardio workouts, finding that they burn more fat than when doing the same exercise within a few hours of having eaten
- Exercising in the morning will make you feel energized and increase your alertness, helping to improve your focus and productivity
- When training before breakfast, you will feel lighter so you will move more easily
- If you train early in the day, your workout will be over and done with so you won’t have to worry about something cropping up that will prevent you from exercising
The Cons:
- Some people find that exercising on an empty stomach makes them feel nauseous
- When exercising without having eaten since the previous day, you may feel weak or even light-headed
- If you want to work out first thing in the morning, you will need to get up earlier
Benefits of Fasted Cardio Workouts Summary
Recent research has shown that fasted cardio workouts do indeed speed up fat loss. However, doubts 
still exist for some.
Perhaps the more relevant question should be not whether doing cardio before eating breakfast will help you to burn fat faster, but whether it makes enough of a difference to warrant doing so.
The bottom line is, if you put in the effort and work out regularly, you will lower your body fat regardless of the time of day you exercise.
If you decide to try a fasted cardio workout, don’t start with anything too intense. Gentle, steady-state cardio such as a brisk walk or a light jog is fine. However, sprinting is not advisable until you see how you cope when running on empty.
The idea is to elevate your heart rate and break a light sweat. Go at a pace that allows you to carry on a conversation. If you’re panting and gasping for breath, you’re going too fast.
