Does Fasted Cardio Burn More Fat

If you have been around on the exercise circuit recently, then you have likely heard of the concept of “fasted cardio” and the idea that it may help you burn more fat than doing cardio traditionally. But what is fasted cardio—and does it actually burn more fat? Let’s take a closer look at what fasted cardio really is and whether or not it really does burn more fat than traditional cardio.

What Is Fasted Cardio?

In the simplest of terms, fasted cardio refers to doing cardio while in a fasting state. For most people who practice fasted cardio, this means exercising in the morning without eating breakfast first; however, some people choose to fast during a different time of the day (such as the afternoon) in order to complete fasted cardio in the evening or at night.

In regards to fasted cardio, fasting occurs around 8 to 12 hours after your last meal. Cardio exercise that is done 8-12 hours after your last meal, but before you eat anything else, is considered to be “fasted cardio.”

The Fasted Cardio Theory

The theory behind fasted cardio is that doing cardio exercise while in a fasting state burns more fat due to the belief that exercising while in fasted state burns stored energy (that is, stored fat and stored glycogen) rather than burning consumed energy (that is, food which was eaten within the last 8-12 hours). According to the fasted cardio theory, burning stored energy results in a greater energy deficit at the end of the day than exercising for the same amount of time but burning only consumed energy.

One additional element to note with this theory is the fact that before you eat food in the morning, your insulin and blood sugar levels will be much lower than they become during the rest of the day. When your insulin and blood sugar levels are this low, there are more fatty acids in your bloodstream, which can then be burned for energy during exercise.

But is there any truth to this theory? Does fasted cardio burn more fat? Or is this another exercise misconception that has taken off due to social media?

Fasted Cardio Burns More Fat: Fact or Fiction?

In order to find out the truth in regards to the question “does fasted cardio burn more fat?” it is important to take a look at the basic facts regarding burning fat and negative energy deficits in the body.

Your body burns energy in order to function: the amount of energy your body burns simply by existing is referred to as your BMR, or basal metabolic rate. This energy is measured in the form of calories. When you exercise, your body burns additional energy by burning through your body’s fatty acids or fat. Your body receives additional energy when you consume food.

In order to lose weight, you must have burned more calories during a 24-hour period than you consumed. For instance, if you consume 2200 calories and only burn 1800 (1400 through your BMR and 400 through exercise) you do not have a negative energy deficit and will therefore gain weight. However, if you consume 1600 calories and burn 1800, you will have a slight negative energy deficit which, if kept up over time, will result in weight loss.

But does fasted cardio burn more fat? The answer is—yes, but with some caveats.

A study from the British Journal of Nutrition found that the participants who exercised on an empty stomach--that is, in a fasting state--burned around 20% more fat than the participants who did not exercise in a fasting state. Another research study found that fasted cardio doesn't just result in immediate fat burning but actually increases the amount of fat burned during the rest of the day--almost twice as much fat burned when compared to people who did the same amount of exercise after consuming food. Some studies have even found that regularly exercising in a fasted state activates fat-burning genes which will make it easier for fat to be broken down and burned off through exercise and diet

Does Fasted Cardio Burn More Fat? Short Term vs. Long Term

However—while these studies did a positive answer to the initial question “does fasted cardio burn more fat?” the final answer is not quite so simple.

While some studies have found that fasted cardio burns more fat compared to cardio done in a non-fasted state, not every study has been conclusive. Some studies which studied the impact of long-term fasting exercise found that over time, the difference between energy burned while exercising in a fasted versus non-fasted state decreased; in other words, the longer that people engaged in fasted exercise, the smaller the gap between the amount of energy burned during fasted vs. non-fasted exercise became.

It is therefore possible that the positive benefits of fasted cardio are better for people who want to kick start their fat loss or otherwise only need to exercise for weight loss during a short term period. People who need to lose weight over a long period of time may benefit from eventually reverting to non-fasted exercise once the benefits of fasted cardio begin to decrease and fall in line with the fat burning ratio of traditional non-fasted exercise.

Final Thoughts on Does Fasted Cardio Burn More Fat?

Does fasted cardio burn more fat? Yes—but probably not over the long-term. While some studies have found that fasted cardio results in a significant increase in fat burned during exercise and even throughout the rest of the day, these positive benefits may not be long term and will decrease over time, resulting in the gap between energy burned during fasted vs. non-fasted exercise to decrease.

While the fat burning benefits of fasted cardio may not be long-lasting, they are still a potentially beneficial idea for people who want to kickstart their weight loss by burning more fat quickly or people who only need to lose weight over a shorter period of time.