Does working out on an empty stomach burn more fat? Should I be doing fasted cardio to see results?

What is Fasted Cardio?

If you google “fasted cardio”, there will be plenty of blog posts with conflicting opinions on whether this form of exercise is effective or not.

Fasted cardio is the theory that doing cardio in a fasted state burns more fat. Some say it is effective while others say it is dangerous. Both are right in this argument. It is effective when you do it right and harmful when you do it wrong. You can burn stubborn fat and you can burn lean muscle. It’s all about doing it the right way to see the best results.

In this article we will discuss: what fasted cardio is/is not, the science of fasted cardio, how to maximize fat burning and not muscle burning, what types of fasted cardio are best and what about fasted weightlifting and more.

What Fasted Cardio is / is Not

Fasted cardio is any type of cardiovascular exercise done in a fasted state.Training on an empty stomach is not fasted cardio. Training in a fasted state is fasted cardio.

Let’s break down what a fasted state is:

Basically, when you eat food, it gets broken down and released into your blood. A fasted state means you have completely digested and absorbed your last meal. Insulin is released and depending on how much food you ate, your levels can remain high for several hours or in a “fed” state. Once your body has finished processing and absorbing the nutrients, your insulin levels drop to a “minimum” level and your body enters that “fasted” state.

So in summary: exercising when insulin levels are high is “fed” training and exercising when insulin levels are low is “fasted” training. A great time to exercise to ensure you’re in a fasted state would be in the morning before your first meal of the day.

Okay now, lets talk about how fat burning relates to these states.

The Science of Fasted Cardio

Your body does not burn fat when it is in a fed state. It stores it. Insulin processes nutrients and breaks down fatty acids. The higher your insulin levels, the less your body is going to use fat for energy.

Your body is going to use the food for energy instead of the stored fat and whatever food it doesn’t use it will store as fat for later. YIKES!

So, if we burn more fat than we store, we lose weight and if we store more fat than we burn we gain weight.

It is important that fasted cardio is paired with a proper diet for it to be effective. Energy balance is the number of calories you consume through food vs. the number of calories you burn though activity. If you are positive energy balance you are consuming more calories than you are burning. If you are negative energy balance you are burning more calories than you are consuming. There must be a deficit for you to see the results you’re hoping for meaning you have to burn more calories than you consume to lose weight.

There are other factors like hormonal balance, stress, sleep, and fitness level also come into play. Counting calories and exercising is not always the only factor.

There are two parts to fat loss: lipolysis and fat oxidation.

Lipolysis is the break down of fat cells. Fat oxidation is the actual burning of fatty acids by cells. A lot of people think fasted cardio is worthless.They think fat oxidation rates aren’t affected in a fed state, just lipolysis rates so all that happens is your body mobilizes many more fat cells than it can actually burn. Research has proven that when insulin levels are high they burn less fat cells in both trained and untrained individuals.

For women, butts, thighs, and hips are probably the most stubborn areas to lose fat. For men, it is your lower abs and lower back. Our fat cells have two types of receptors; beta-receptors which speed up fat burning, and alpha receptors that hinder it. The alpha receptors are in those trouble spots, making them more “resistant” to being mobilized.

The more beta receptors a fat cell has, the more “receptive” it is to fat burning. The areas that lose fat quickly are the ones with more beta receptors and the areas that do not are alpha receptors. Those areas also have a problem that relates to blood flow. If you have ever noticed that your trouble areas are colder to touch than your tighter areas this is because there is less blood flowing through there.

So how does fasted cardio help?

Blood flow in the stomach area is increased when you’re in a fasted state, which means catecholamines get burned easier.

Catecholamines are chemicals that break down fat cells into usable energy. They travel through your blood and attach to fat cells, which trigger the release of the energy stored within the cells so it can burn off.

What Types of Fasted Cardio are Best?

“High-Intensity Interval Training” is ranked number one by many studies that have proven shorter sessions of intense cardio results in more fat loss over time compared with longer, steady sessions. Research shows that it increases your metabolism, improves insulin sensitivity, increases your muscles’ ability to burn fat for energy, elevates grow hormones, and decreases post-exercise hunger.

By keeping cardio sessions short, it will help you persevere muscle and strength because the longer you train in a fasted state, the more muscle you potentially lose. This type of cardio uses your body’s twitch muscles, which have metabolism and hormonal benefits. HIIT will improve your cardiovascular health more than any other exercise. It can be done as sprints, stair-master, rower, jump rope, bike, or a combo of cardio and strength drills.

The point is to keep it short and intense.

HIIT is also known for the “afterburn” effect.

Meaning after your workout is finished you still burn additional calories for up to an hour.

What About Fasted Weightlifting?

Weightlifting fasted is worthwhile because it causes an increase in plasma catecholamine levels (the chemicals that break down fat) which makes them able to mobilize fat better. You may feel weaker during your first couple weeks beginning the fasted weightlifting because carbohydrates improve your performance in the gym immensely.

As your body slowly adapts to training in this fasted state, it will learn to preserve glycogen and better preserve your performance. If you’re looking to get rid of stubborn fat, fasted weightlifting definitely works faster compared to a fed state.

How to maximize fat burning and not muscle burning:

One question that comes up often is will this promote the loss of lean muscle mass?

We get it, the last thing you want to happen is that all your hard work starts disappearing from your body.

Exercising in a high intensity fasted state can lead to burning muscle mass. If you damage and break down too many muscle cells in your workouts, your body will not be able to keep up. Fasted cardio is for losing fat faster. It is not so good at maintaining muscle but can be done if you do it right.

To maintain muscle mass and keep your body burning fat, you should use a moderately strong calorie deficit and eat high protein meals. It is also important to pair resistance training with fasted cardio either after your cardio session, or in-between cardio days. Lastly, do not do more than four-session per week, and no more than 30 minutes per session.

Supplements

It is highly recommended to add supplements into you fitness regimen in order to increase the benefits of fasted cardio while eating a balanced diet. Caffeine, a natural supplement, increases energy and therefore increases the amounts of energy your body burns in a day. It also improves strength, promotes muscle endurance, and enhances anaerobic performance.

Another supplement is BCAAs or . This will help prevent muscle loss and will reduce the amount of time your body needs to recover from a workout. It will also help increase strength. It also has no effect on insulin levels and won’t break your fasted state like food before your workout.

Gym Junkies also has some great supplements that pair with fasted cardio, you can find them here.

Conclusion

Although to lose fat and get lean you don’t have to train fasted, it is definitely an effective fitness regimen that shows results. This is especially valuable for those that are already somewhat lean because you will be dealing with that stubborn fat that can take awhile to disappear with just regular diet and exercise.

Once you try HIIT training in a fasted state you will see remarkable results and finally burn that excess fat you been hanging on to and your endurance will improve tremendously.

Fat loss is a whole-body process and by focusing on what your goals are you can determine whether adding fasted cardio is going to be effective for you.

-Megan Heaton