Best Cardio for Fat Burning: Low Intensity or High Intensity?

Simply looking at the amount of fat burned during exercise is shortsighted. Fat burning must be considered over the course of an entire day.

Q: I was told that low-intensity cardio is better for fat burning than high-intensity cardio. True or not?

A: Not!

It is true that aerobics performed at a low intensity (60 to 80 percent of max heart rate) burn a greater percentage of fat calories than higher intensity activities (which is why low-intensity cardio is called training in the “fat-burning zone”). The problem is, burning a greater percentage of fat doesn’t necessarily equate to burning more total fat calories. Consider the following as an example:

Suppose you walk on the treadmill for a half-hour and burn a total of 150 calories. Of these calories, say 60 percent comes from fat. This would mean that you’ve burned a total of 90 fat calories from the low-intensity cardio. Now, let’s say you run on the treadmill for that same half-hour, which might burn 300 calories with only 40 percent coming from fat. Well, the percentage is lower, but you’ve actually burned 120 fat calories in that same half-hour!

What’s more, not only is fat burning maximized during high-intensity activity, but there is also a bigger increase in excess post-exercise oxygen consumption (EPOC) – the amount of calories burned once the activity is finished. EPOC is intensity dependent … the more vigorous the exercise, the greater the after-burn. If you’re really training hard, this can keep your metabolism elevated long after you’ve stopped working out and have a significant effect on the amount of fat metabolized.

It’s also important to note that the human body is a very dynamic organism and continually adjusts its use of fat for fuel. Substrate utilization is governed by a host of factors (including enzyme levels, substrate availability, internal feedback loops, etc.) and these factors can literally change by the moment. Thus, simply looking at the amount of fat burned during exercise is shortsighted. Fat burning must be considered over the course of an entire day – not on an hour-to-hour basis – to get a meaningful perspective on its impact on body composition. And on this basis, high-intensity cardio always comes out ahead.

Bottom line: High-intensity exercise burns more fat calories on an absolute basis than lower intensity activities, making it the preferred choice if you’re looking to optimize fat loss.

Brad Schoenfeld, Ph.D., CSCS, CSPS, FNSCA is an internationally renowned fitness expert and widely regarded as one of the leading authorities on training for muscle development and fat loss. He is a lifetime drug-free bodybuilder, and has won numerous natural bodybuilding titles. He has published over 60 peer-reviewed studies on various exercise- and nutrition-related topics. Brad is a best-selling author of multiple fitness books including The M.A.X. Muscle Plan (Human Kinetics, 2012), which has been widely referred to as the “muscle-building bible” and Strong and Sculpted (Human Kinetics, 2016), which details a cutting-edge, body-sculpting program targeted to women. Brad also has authored the seminal textbook Science and Development of Muscle Hypertrophy (Human Kinetics, 2016), the first text devoted to an evidence-based elucidation of the mechanisms and strategies for optimizing muscle growth. In total, Brad’s books have sold over a half-million copies. For more information, visit For more information, visit

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