6 Surprising Benefits Of High Intensity Interval Training (HIIT)

Superior fat loss, increased human growth hormone, and improved insulin sensitivity, Oh My! Let’s look at how HIIT can help with all this.

Till now, the most effective form of exercise I knew of was running (my version is more like “trotting”). For years I hated it, but recently developed a better enjoyment, mostly because I needed to. The results were superior to anything else I’d tried.

But jogging is not only hard on the body, it’s time consuming. In order to keep up with the results I’d have to add weight lifting and more mileage, equating to… more time. Many of us have succumbed to the idea that a healthy fitness regimen requires at least 45 minutes to an hour per day, several days per week. I’d gotten so good at sucking it up for my 5-7 mile run, I was almost disappointed to hear that there’s a better, faster, stronger, more effective fitness strategy on the market, and it’s free.

Happily, I got over it. High Intensity Interval Training (HIIT) is now rocking my world, and revolutionizing fitness training.

What is HIIT?

We used to think that aerobic activity was king for fat burning. Aerobics are mostly low-intensity cardio at a steady pace. Your heart rate maintains about 60-80% of its maximum usually for 30+ minutes. Marathon runners will cover tens of miles over several hours. They tend to be very thin, but this type of workout is also “catabolic,” meaning it can and does cause the breakdown of muscle.

HIIT capitalizes on the benefits of anaerobic exercise. Anaerobic literally means “without breath.” Your heart rate reaches 80-90% of its maximum. It’s quick and strength-based, involving bursts of intense exertion followed by brief times of rest. If you can do an exercise for more than 2 minutes without stopping, consider it aerobic. Anaerobics include sprints, speed pushups, jumps, and all non-endurance activities that increase strength, power, speed and muscle mass.

HIIT Superior For Fat Loss

During aerobic exercise our bodies burn more fat than glycogen and this looked like the way to go because during anaerobic activity, the fat/glycogen ratio is lower. But it turns out that anaerobics burn way more fat overall. Because HIIT involves bursts of output with intermittent times of rest, you don’t just burn out at the end of a sprint, but recover and come back again, making it possible to accomplish more with several sets in 15 minutes that one set in an hour.

HIIT and The Afterburn Effect

I’ve heard it said that one session of HIIT can increase metabolism for an additional 24 hours or even up to three days afterwards. After I started trying it, I found that highly believable just because of the way I felt. My energy has been amazing. But there’s also science to back it.


Marc Perry, CSCS, CPT interviewed “Dr. Christopher Scott, PHD, who is an exercise physiology professor at the University of Southern Maine and one of the world’s foremost experts on the Afterburn Effect, which is calorie burn AFTER exercise.”

Scott postulates that although mostly glucose is burned up during the period of exertion, the body then resorts to fat stores for the energy needed to recover. He also suggests that as much as 95% of the calorie torching effects of HIIT happen after your work out. We don’t yet know any exact estimates for the afterburn effect, but he does affirm what we’d have hoped: that the greater the exertion, the greater the after effects. “For example, sprinting as fast as you can for 30 seconds for 5 rounds will have a much larger afterburn effect compared to jogging for 30 minutes.”

In fact, Scott says that a long, steady-paced jog hardly if at all triggers the desirable afterburn.

More Benefits of HIIT

Studies show that HIIT has several other benefits besides extremely efficient fat burning, such as these:

  • HIIT actually triggers a huge boost in production of HGH (human growth hormone), also tagged “the fitness hormone”
  • Increases insulin sensitivity, according to one study by Michael Mosley, as much as 24% in four weeks (as reported by BBC)
  • Improves aerobic capacity
  • Builds muscle mass


It may take time to build up to a high level of intensity. If you have any health conditions, as always, consult first with your physician. It’s intelligent and effective to start slow if you need to, particularly if you have had any previous injuries, are out of shape, or have serious conditions such as hypertension or heart disease. The key is not to go as hard as your professional trainer, but to go to your “edge,” and then slightly past your edge. It may be a bunch of discomfort for a very short time, with a long term payoff.



High Intensity Interval Training (HIIT): Best Cardio to Burn Fat by Marc Perry. BUILTLEAN. http://www.builtlean.com/2010/06/04/high-intensity-interval-training-hiit-best-cardio-to-burn-fat/#fn-961-6

Too Busy to Exercise? Get Fit in 3 Minutes a Week by Dr. Mercola http://fitness.mercola.com/sites/fitness/archive/2012/04/06/high-intensity-training-benefits.aspx

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