fasted cardio and fat loss
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Fasted cardio for fat loss

Something that increased a lot in popularity lately fasted cardio. People claim that it burns more calories and fat doing cardio on an empty stomach, but are they right?

Fasted cardio and fed

Let me first start off with defining fasted and fed cardio. Fasted cardio is doing a cardio session without having eaten in a while.

Most people are only in a fasted state while they are sleeping. However, there are some people that make a conscious effort to extend their fasting time.

This is called intermittent fasting and it is not a dietary change, but a lifestyle change. You decrease the time you eat in a day.

The most popular approach is the 16/8, which means you fast 16 hours a day and eat 8 hours a day.

Fed cardio is doing cardio after you consumed calories. So after your first meal.

So how did fasted cardio become so popular and where did it come from? Well, it all has to do with insulin levels. These are the lowest first thing in the morning.

Insulin and fasted cardio

Insulin is a hormone that is considered to be the main anabolic hormone of the body. Its role is to regulate the metabolism of the macros but especially glucose.

And can convert glucose into glycogen and glycogen into body fat.

The level of insulin spikes after you eat something, it does this with everything you eat (protein, fats, and carbohydrates). But peaks higher after eating glucose.

When your insulin levels are high, your body will use carbohydrates as the main fuel source for your workout.

This way there is not a chance for body fat to get burned as an alternative fuel source.

The idea of fasted cardio can also come from the fact that glycogen levels (the carbohydrates stored in your body) are lowest in the morning. So you start to use fat instead of carbs for fuel.

And for both idea, there is scientific evidence to support them. (1) (2)

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The studies that I mentioned above are not wrong. However, it is important to note that yes, fasted cardio burns more body fat during the cardio session.

It is important to note that after the cardio session your body will burn less body fat and more carbohydrates for the upcoming 24 hours.

So the energy source get’s switched around.

With fed cardio, it is the exact opposite. You’ll burn more carbohydrates during the cardio session, but less the next 24 hours. Instead, you’ll burn more body fat in that period.

Fasted cardio and fat loss

There is no significant difference when it comes to overall fat loss when looking at fasted or fed cardio.

However, there is still more research necessary to certify this completely. There are some small studies that indicate that there might be a small advantage for fasted cardio.

And this advantage would only apply to certain specific groups. With specific groups, I mean elder, trained athletes, women, etc…

But right now there is no clear evidence that one of the two will make a significant impact on your weight loss. (3)

What does cause more fat loss?

Right now, you might be wondering. What does cause more fat loss then? Well, the most important thing you need for fat loss is a calorie deficit.

You can create a calorie deficit is two ways. One being adjusting your diet, and the other one by increasing your total daily energy expenditure, also known as increasing your exercise.

I would always advise looking at your nutrition first, this is the easiest way to create a calorie deficit.

Start off with a deficit of 200-300 calories, this already starts the fat burning and allows you to increase this whenever you hit a weight loss plateau.

You can create your deficit by doing cardio or exercise, but this is really unsustainable. Just imagine that your gym closes for a week. Or you get injured. What are you going to do then?

When it comes to weight loss you can do cardio either way. Some people prefer to do it fed and some fasted. Do whatever you prefer and makes it easier to sustain.

Fasted cardio and glucose tolerance

Untill, now there hasn’t been a clear benefit to fasted cardio except personal preference. However, there is on benefits that you need to know of before you make your decision.

The benefit of fasted cardio is the improvement of your glucose tolerance. (x) This is great, especially for those struggling with this.

Because it is correlated with type-2 diabetes, an increased risk of cardiovascular disease, and insulin sensitivity.

Next to that impaired glucose tolerance is also a risk factor for mortality.

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Why cardio might not be the answer

The majority of people start doing cardio when they want to lose weight. And this is great because cardio has a lot of health benefits.

But for weight loss, it won’t give you the results you are expecting. That is for a few reasons.

The first reason is that people overestimate the number of calories they burn during a session. Most cardio machines drastically overestimate the number of calories you burned.

This way it is really hard to know if you are actually in a calorie deficit or not.

This ties in with the second reason, being that there is a big chance you’ll eat back the calories, you think you burned.

You think you burned 500 calories on the treadmill, but you only needed to burn 200. So you eat 300 calories extra because that fits into your diet today.

However, you actually only burned 200 calories and now you are in a 100 calorie surplus.

Next, to all this, it is also a really unsustainably way to create your calorie deficit. So focus on your nutrition first, and then add some cardio.

Here are some blog posts where I help you change your nutrition to give you the best and fastest results! How to setup your fat loss program, fat loss 101, fat loss habits to lose weight, and the most common diet mistakes.

Thank you for taking the time to read my blog, let me know in the comments what you like best, fasted or fed cardio?

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