When it comes to cardio workouts, do you know if low-intensity or high-intensity is better for burning fat? Most likely you’ve heard the debates surrounding this subject if you’ve been into health and fitness for a while.

We will clear up once and for all the many myths surrounding the topic of “what intensity level is better for burning body fat?”

This is one of the most asked questions by the clients of personal trainers.

If you were to ask 100 people which approach is better, you’d probably get 100 different answers.

Let us shed some light so that you can get a better understanding…

The Laws of Thermodynamics and Energy Conservation

The first law of Thermodynamics states, “Work and heat are mutually convertible(can be converted from one form to another).

The change in a system’s internal energy is equal to the heat absorbed (calories in) from the environment minus work done (calories out) on the environment.”

The law of Energy Conversation states, “Energy cannot be created or destroyed but may be transformed from one form to another.”

Those two laws simply mean energy in equals energy out.

In other words, if you want to maintain your current body weight, the number of calories you consume must equal the number of calories you burn.

If you want to gain weight, the number of calories you consume must be roughly 20% greater than the amount that you burn.

Lastly, to lose weight the number of calories that you consume must be roughly 20% less than the amount that you burn.

How does this apply to cardio intensity?

Well, regardless of whether or not you are using a low-intensity (e.g. 60% of your maximum heart rate) or high-intensity (e.g. 80-85% of your maximum heart rate) cardio, because the energy in equals the energy out.

Some people seem to believe that higher-intensity cardio burns more fat, but it doesn’t.

Higher-intensity cardio allows you to burn more calories in a shorter period of time and is beneficial when you have a limited amount of time to spend in the gym.

Several studies have proven that low-intensity cardio and high-intensity cardio burn roughly the same amount of weight/fat. Once again it’s based upon the simple laws of Energy Conservation and Thermodynamics (calories in and calories out).


Now you know the cold-hard facts about intensity as it relates to cardio training.

High intensity or low intensity, one is no better than the other in burning fat. What matters most is the total number of calories you’ve taken in compared to the amount burned at the end of each day which determines your physical progress.

As a friendly reminder, your diet is roughly 80% responsible for your physical appearance.

Garbage in equals garbage out!

Healthy foods equal a healthy output from your body.

Healthy foods mixed with moderate amounts of your favorite junk foods equals the best of both worlds. You can enjoy a fit lifestyle and continue eating the foods that you enjoy most.

So when someone attempts to argue with you on which intensity level is best for burning fat, you can now present him or her with the science that shatters all those myths surrounding this subject.

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