Fasted Cardio: Benefits, What It Is & How To Do It In 2024

Some people love high-intensity interval training because it’s great for burning body fat. Others don’t need to burn calories—they’re in it for muscular body mass, plain and simple. 

Resistance training and even moderate-intensity exercise without those vital glycogen stores, however, may compel the human body to burn more fat and muscular tissue than it would in a fed state.

Does the food that you eat before high-intensity exercise have an impact on the calories burned after the fact? Can you maintain muscle mass even in a fasted state? Learn all about fasted cardio in this beginner’s guide.

What Is Fasted Cardio?

Fasted cardio is simply the act^[1] of participating in fat-burning cardiovascular workouts on an empty stomach. A fast is usually 12-24 hours where you can have nothing but zero-calorie beverages like water, black coffee, and tea.

Lots of people prefer cardio in the morning for this reason—with one’s diet out of the way, some find that they feel lighter, brighter, and more excited to sweat. Plus, the low blood sugar that is likely to come as a result will usually give you a great appetite for breakfast.

How Does Fasted Cardio Burn Fats?

Fasted cardio can help you burn stored fat through lipolysis, the breakdown of fatty tissue, and fatty acids for fuel. 

Your body uses two main sources of fuel for exercise: glycogen stores and fat stores. Fed cardio supplies your system with more calories than cardio in a fasted state. Targeting stubborn fat, in many cases, becomes a matter of limiting the availability of new fuel, so that the body burns fatter already stored instead. 

Building muscle, on the other hand, might be difficult under these circumstances, even if you’re using a fat burner for weight loss. Does fasted cardio lead to less effective strength training and fewer healthy gains?

How Long Should You Fast Before Fasted Cardiovascular Exercise?

There is no standardized fasting period for everybody—instead, you should observe how your body responds to various intermittent fasting plans geared toward your workout. Have you eaten breakfast? Was it a balanced meal? 

Regardless of the exercise performed, there is no dispute among fitness professionals: fasting periodically is really, really good for you. 

Does Fasted Cardio Reduce Muscular Mass?

Adequate nutrition, protein intake, and a great session are all that our bodies need to become something incredible. What happens when you leave yourself without the fuel that you need to succeed?

Fasts before exercise increase^[2] your body’s fat-burning potential and decrease total body fat percentage by inducing a faster rate of fat oxidation. This tendency to burn fat much more efficiently might, however, carry over to skeletal muscle,^[3] including the major muscular groups that you’re interested in pumping up to the max.

Muscle protein synthesis is stimulated^[3] by the presence of new amino acids entering the body. When we consume less than normal, this threshold actually increases, further impeding the body’s ability to produce new muscles, especially after a high-intensity workout on an empty stomach. 

Nutrition, in any case, appears to be a vital aspect of this process. Will a fasted workout completely undermine your fitness goals if fat loss isn’t your primary intention?

Benefits Of Fasted Cardio

The benefits of the fasted cardio workout go beyond those of skipping breakfast alone, plain and simple, but they’re all just as relevant and worth mentioning^[4]:

• A fasted state gives the body time to cleanse itself of impurities, flushing out your system
• Fasts keep your body healthy by helping it ward off chronic disease
• Fasting is great for weight loss in a general sense

Even if you’re not interested in the fat-burning benefits of a fasted window, it might be something to try if you’re watching your carbohydrate (carb) intake, insulin levels, or even your fat, protein, and carb intake. If eating breakfast or dinner isn’t a huge priority for you, we can definitely recommend sitting on an empty stomach during the fasting window most convenient for you.

Risks Of Fasted Cardio

While an overnight fast is something that we’re all used to, research suggests that an extended fasted cardio session may end up limiting the benefits that you stand to enjoy at the gym, especially if a bigger, stronger, and more powerful physique is what you would like to achieve. 

This study^[5] conducted by the British Journal of Sports Medicine on the workout-enhanced performance of Muslim athletes fasting during Ramadan notes a significant reduction in speed, agility, and endurance. Fasted cardio and disruptions in their ordinary sleeping patterns prevented them from maximizing each workout as usual.

Your muscular gains may not be all that you have to lose if you push it to the limit:

• A significant calorie deficit may leave you feeling woozy, fatigued, unfocused, and burned out
• Fasted workouts may give you less energy to exercise, as well as less energy after your workout
• Long-term fasting may impair^[6] your athletic performance
• In terms of women’s health, fasting at length may lead you to lose weight and disrupt your menstrual cycle, opening the door to long-term reproductive health conditions later on down the line
• And, of course, depending on your energy expenditure and body composition, fasted cardio may hinder muscle-building, especially if you’re partaking in high-intensity training

If you find that eating prior to a sweat session results in twice the amount of energy and interest, fed workouts may simply be the way to go. There is no reason to force fasted exercise on yourself if you’ve been consistently trained traditionally and perform adequately while digesting food.

There are many great approaches to losing fat without gaining muscle; not eating for prolonged periods of time isn’t necessarily the only way to a happier, healthier body.

Is Fasted Cardio Better For Weight Loss?

If burning fat cells is your ultimate goal, fasting before cardio is the most effective route to fat loss in every part of the body. 

It doesn’t necessarily need to feel like a requirement or a punishment—even trying it out once a week may be enough to kick-start your fitness journey. Don’t knock it until you try it.