High Intensity Interval Training (HIIT) for Fat Loss


For years, we have been told that the best form of exercise to help you lose weight is a long duration, low intensity cardio activity. We’ve been told that we needed to stay in the “fat burning zone” if we wanted to burn fat, and that venturing outside of this “Holy Grail of Zones” would be counterproductive to our weight loss goals.

Is there such a thing as this “Zone of Legend”, and do you really need to spend an hour or more trudging away on the elliptical to burn body fat?

The fat-burning zone is not a myth.

Your body has two primary sources of fuel for all bodily processes: fats and carbohydrates. When you are exercising, you are burning calories, and a certain percentage of those calories are burnt due to the utilization of fat, and others are due to the utilization of carbohydrates.

When at rest and during low-intensity exercise, a higher percentage of the calories being burned are coming from fat utilization. The more intense your activity becomes, the more carbohydrate your body must utilize to fuel it. So yes, there is an exercise intensity at which you can work where the highest percentage of fat will be utilized; however, you must exercise at this intensity for so much longer to burn any significant amount of calories.

I don’t know about you, but I don’t have an hour or two to spend on the treadmill every day, in addition to my strength training. I would much prefer to spend only 20 minutes on “cardio” and still get the same benefits, and this is where high intensity interval training (H.I.I.T.) comes in.

HIIT manipulates work-to-rest ratios and exercise intensities to maximize benefits in a shorter amount of time. You work really hard for a set duration of time then recover for another set duration, then you repeat.

Depending upon your fitness level, the work period can be shorter or longer. The shorter the work period, the harder you should be working and the more recovery time you should allow.

In contrast, the longer the work period, the less intense it will be and shorter the recovery period should be. Training in this manner elicits what is called an afterburn effect.

Basically, you create a huge metabolic disturbance during exercise that it takes your body up to 36 hours post workout to return to normal. This means that you are burning a greater amount of calories at rest during that 36-hour window.

Anaerobic High Intensity Intervals

Anaerobic High Intensity Intervals utilize your anaerobic energy system. When working in the anaerobic energy system, the work period will max out at about 30 seconds.

An example would be a 30 second maximum effort sprint followed by 2 minutes of walking to recover. You could repeat this interval 4-6 times.

5 minutes for a warm-up, 10 minutes of interval work and 5 minutes for cool-down would be a 20 minute workout.

This is a much more efficient use of time for the busy individual than spending an hour on the treadmill!

Aerobic High Intensity Intervals

Aerobic High Intensity Intervals utilize your aerobic energy system. An example of an aerobic interval would be a moderate intensity jog for 4 minutes followed by 1 minute of walking to recover. Again, repeat this interval 4-6 times, and you have 25-30 minute metabolically efficient workout.

Tabata Intervals

Tabata intervals have received a lot of media attention thanks to group exercise classes and boot camps. Tabata is the name of a person, and his interval protocol calls for 20 seconds of true maximum effort followed by only 10 seconds of rest, repeated 8 times.

When done properly, this 4-minute protocol can elicit the same cardiovascular adaptations as a running 3 miles, plus it’s a much more metabolically efficient workout.

The catch is, you must maintain maximal effort with each subsequent interval. If you slack on the intensity, then you will not get the full benefits.

So, if you’re tired of spending hours upon hours each week doing traditional “cardio” with little results to show for it, maybe it’s time you H.I.I.T. it!  As with starting any new workout, make sure to check with your physician before incorporating high intensity training.

About the author

Katie Brumley
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Katie is the Strength & Conditioning Coordinator at the Baylor Tom Landry Fitness Center in Dallas, Texas and a certified personal trainer through the National Strength & Conditioning Association.

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High Intensity Interval Training (HIIT) for Fat Loss