Low-Intensity or High-Intensity Cardio for Fat Loss?

Who has not asked themselves this question? You are in luck. I’ve gone on this hunt for truth just for you.

The misconception about low-intensity cardio:

“It burns more fat than high-intensity training” or does it?


It is true that a greater percentage of calories burned will come from fat if exercising at a low intensity.


because you’re exercising at a lower intensity, you will burn less total calories.

Less calories burned = less weight loss

How does it all work anyway?

Carbohydrates and fat are the body’s primary fuel source during activity. Carbohydrates are used first and in terms of carbohydrate sources, it will first be blood glucose that’s utilized for energy.

Next, stored carbohydrate (glycogen) will be turned into glucose and utilized. As exercise continues (for a long, long, long time), fat will become the primary fuel source.

It is also important to note that fat requires oxygen to be burned as fuel, which is where the misconception about low intensity aerobics burning more fat comes into play. The thought is that if you have more oxygen available (e.g., you’re not gasping for air because your intensity is so low), you’ll be able to burn more fat.

So what’s the problem with this theory?

The body does burn a higher percentage of calories from fat in the ‘fat burning zone’ or at lower intensities.

But, at higher intensities, you burn a greater number of overall calories, which is what you should be concerned with when trying to lose weight.

The chart below details the fat calories expended by a 130-pound woman during cardio exercise:

Intensity Level                                 Low Intensity                       High Intensity

Max Heart Rate (MHR)                          60-65%                                   80-85%

Total Calories in 30 min.                             146                                         206

Total Fat calories in 30 min.                        73                                           82

As you can see, the woman burns more total calories and more fat calories at a higher intensity.

So what am I trying to say? Low-intensity cardio is worthless? Absolutely not!

There is no “best” duration or frequency to do cardio, except the amount it takes you to get the results you want. That amount is not determined by opinion, committee, formula or even by scientific studies. What works for someone else, doesn’t have to work for you and vice versa. You are your own “scientific study.”

“Oh Great, you say. I’m on my own?” Not at all. Listen to your body. If it works, stick with it but if it doesn’t, you have to mix it up. If you do what you’ve always done, you’ll get the results you’ve always gotten.

My recommendation:

Consider doing a low intensity/long session, a high intensity/short session and a few medium intensity/ medium length sessions. Keep your body guessing. This ensures that you work on endurance and that you work in multiple heart rate zones. The entire heart rate zone for fat burning is a HUGE debate. In another article, I’ll discuss the importance of Heart Rate. Stay tuned

Stay Happy & Healthy

– Dr. Maria


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