Exercising on an empty stomach is a staggering fitness movement that has many of us a little baffled. Just like the high carb vs low carb diet debate, the fasted vs non-fasted debate is equally contentious. Before you start working out on an empty stomach, read this article to be aware of the possible positives, as well as negatives of this choice.
Fasted state exercise (also known as fasted cardio) is when you work out on an empty stomach, which is usually performed in the morning before you eat breakfast. This normally takes several hours for our body to enter a fasted state.
Fed cardio is the reverse, which is a workout after a meal when your body is digesting the nourishment and absorbing the nutrients. Our energy demands are met by the food we are digesting.
The two main arguments are as follows. First, working out first thing in the morning before eating breakfast will burn more fat as the body is in a fasted state. Therefore, it will contribute to greater weight loss. However, this could have a negative impact on your workout as you’ll have less energy. Thus, working out after a meal could give you a boost in energy and contribute to a better workout.
So, which is the superior method? Below, we’ve cut through the confusion by breaking down the pros and cons of fasted cardio vs. fed cardio.
Does Working Out on an Empty Stomach Burn More Fat?
Working out on an empty stomach, in theory, is beneficial. This is because, after an overnight fast, your glycogen stores are considerably reduced and the insulin levels induce the body to transfer energy utilization away from carbohydrates which enables greater use of stored fat for fuel. In turn, this leads to a higher level of fat loss.
According to research conducted in 2016, thirty-four resistance-trained males were split into two groups: the time-restricted feeding (TRD) group fasted for 16 hours and consumed 100% of their energy needs in 8 hours, in a day, and the normal diet (ND) group fasted for 12 hours and consumed 100% of their energy needs within 12 hours in a day. Both groups consumed equal calories and were matched for macronutrient distribution.
Results suggest that the TRF group has overall experienced a decrease in fat mass (from 13% to 11%), whilst maintaining muscle mass. Moreover, these individuals’ health-related biomarkers improved.
An empirical study evaluated the effects of aerobic training in a fasted versus fed state during Ramadan on the body composition of 19 physically active men. The data indicate that Ramadan fasting and aerobic exercise practiced in a fasted state reduces body fat, along with improving lipid profiles.
On the other hand, a 2014 study investigated the changes in fat mass and fat-free mass in a four-week period. Twenty young females were split into two groups: the fasted cardio group, and the fed cardio group. Both groups are fed at a 500 calories deficit, consume the same amount of macronutrients, and do 1 hour of moderate-intensity cardio, three times a week.
After four weeks, both groups lost a significant amount of fat but found no difference in fat loss between the groups. This implies that fasted and fed cardio are equally as effective!
Benefits of Fed Cardio
Below, we’ve listed some of the main benefits of fed cardio (i.e., exercise in a non-fasted state).
Have you ever heard of a pre-workout meal? If not, this is when you consume calories before a workout. Usually, this comes in the form of sweet, glorious, carbohydrates! Carbs help boost your glycogen stores which in turn provides you with more continuous energy during your workouts, allowing you to train harder and for longer. This goes for not just cardio, but also strength movements such as standard pushups or pull-ups.
No Time Restriction
Fed cardio enables you to work out at any time of the day irrespective of how much food you’ve consumed. This allows greater flexibility to your day in comparison to a fixed training regiment where you would do fasted cardio in the morning. You may not be a morning person, and your physical performance isn’t at its peak in the AM.
Usually, it may take several hours after you’ve had your last meal to finish digestion and enter a fasted state. The time differs between individuals but, normally, 12 hours is the estimate. Therefore, you could be restricted to a certain workout time.
Reduce Protein Breakdown
Protein breakdown occurs during work out where your muscles are being broken down for energy. Therefore, to gain as well as maintain muscle, protein synthesis must be at a minimum equal to the rate of protein breakdown.
The Final Word
The practical takeaway is that, for fat loss, there doesn’t seem to be any special benefit to doing cardio fasted. The magnitude of fat loss is mostly determined by your caloric deficit. In other words, when you consume fewer calories than what your body needs.
A systematic review and meta-analysis that looked into 5 independent 4-6 weeks trials have found that a fasted in comparison to fed exercise does not increase the amount of weight loss and fat mass loss. Rather, weight loss and fat loss from exercising are contingent on one’s caloric deficit over time, rather than fasted or fed cardio.
It all comes down to your personal experience and goals. Some people may prefer to do fasted cardio because they don’t have the appetite to eat in the morning. This routine could help them be more energized for the day. Moreover, having a meal before a workout could simply be inconvenient for some of us, and this is perfectly fine! The bottom line is that either method could work for you, depending on your preferences, lifestyle, and your ability to sustain a caloric deficit using one approach or the other.
I’m Pat Chadwick, a qualified Level 2 and Level 3 calisthenics coach and athlete from London, England, with six years of experience. I’ve competed in various UK competitions, including the Kalos Stenos Championships, where I achieved third place in the lightweight category. My passion is highlighting the beauty of calisthenics as an authentic and pure form of body expression. I believe that everyone has the potential to become a champion of their body and mind, and that calisthenics opens the door to personal empowerment.