Does The Fat Burning Zone Still Exist?

Last week I was at a spin class, and the instructor had us do a steady ride for a song or two, and said we’d be burning more calories in this aerobic pace because we were in the fat burning zone. Then she said we should come to her endurance ride because it would be 90 minutes in the fat burning zone. I was thinking to myself, “Wait what? Is the fat burning zone still a thing?” I haven’t heard that terminology in forever, so I started doing some research…aka Googling :-P

Does the fat burning zone still exist? Or is HIIT better?

From what I remembered, the fat burning zone was maintain your heart rate at a certain rate in order to burn the most fat/calories. So why is this the case, supposedly? Here’s a great explanation from Active:

The fat-burning zone is a concept that the body burns a greater amount of fat at lower-intensity aerobic exercise than it does at higher intensities. Actually, the body burns a greater percentage of fat at lower intensities than at higher intensities. At lower intensities the body may burn 50 percent of the calories from fat, while at higher intensities it may only burn 35 percent. But at higher intensities you burn way more total calories—and more fat calories overall—than you do at lower intensities.

Very interesting. And that’s what I was thinking in the class. We did a lot of hill rides and sprints and in my mind, that probably burns more calories overall than a steady pace. Furthermore, us runners know that the more you do something at a certain pace/rate, the more your body adapts. If you’re in the aerobic zone for every workout for months, eventually you will plateau. Speaking of plateau, I wrote about a few ways to beat that pesky plateau a while ago.

Let’s also talk about the afterburn effect. You may have read in plenty of fitness magazines that the reason HIIT (high intensity interval training) is so beneficial is because of the afterburn. For hours after you’re done exercising, your body continues to burn calories, whereas after aerobic exercises, there isn’t much of an afterburn. In a study done by the University of Maine, “A low intensity exercise group cycled at a steady rate of 3.5 minutes. The higher intensity exercise group required three 15 second sprints as fast as the subjects could run.”

What were the results?

The cycling group burned 29 calories vs. 4 calories for the sprinting group during the exercise. But when you take into account the calories burned after exercise, or the afterburn effect, the numbers look much different – 39 calories burned for the cycling group vs. 65 calories burned for the sprinting group. A surprising 95% of the total calorie burn occurred after the sprinting exercise!2 Keep in mind the cycling group exercised for almost 5x longer than the sprint group (3.5 minutes vs. 45 seconds).

I’ll admit, sometimes when I do a quick hill sprint session on the treadmill and I’m done in 15-20 minutes, I feel like I should keep exercising. But it’s clear that HIIT training really does have more “bang for your buck.” Why slog along on a treadmill for hours (okay maybe that’s an exaggeration) when you could do circuit training or HIIT and be done in 20-30 minutes (and reap the same benefits if not better)?

Obviously, this all doesn’t relate to those of us who are training for a long distance race. That is always the conundrum I have. I want to burn more fat and get leaner, but I’m be training for a half marathon or a marathon, so long, steady state cardio is my life at the moment, other than track workout or tempo days. Though I have started doing circuit training for strength workouts that are high intensity and last 30 minutes. I’ve loved it so far, and it’s a good change of pace from my usual lifting routine. Here’s an example of a workout I do.

Have you heard the term “fat burning zone” used recently?

What do you think of it vs. HIIT?


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  1. This is really interesting and while I have trouble wrapping my brain around how this all works in the body, your writing makes sense. I agree, I never feel “done” after a HIIT workout, but it does sound very effective in terms of calorie burn. I wonder the effects on muscle mass?
    Alisa @ Go Dairy Free recently posted…Chocolate Cherry Cashew Granola Bars (aka Homemade Kind Bars)My Profile

  2. I don’t do a TON of cardio (I like weights) but when I do it is DEFS HIIT. I totally agree, why would I spend hours on a DREADMILL when I can get awesome results in less time! Great post!

  3. The explanation you found from Active is right on, but regardless of whether or not you’re in the “fat burning zone”, if your goal is weight loss, the most important thing is that you’re burning more calories than your taking in. Plus, any sort of exercise is good! Whether your going slower longer or faster for shorter, as long as your moving, you’re doing your body some good :)
    Nicole @ Fitful Focus recently posted…Fit, Focused, and Fun Finds (from around the web!) #27My Profile

  4. There are so many fitness “trends” right now for fat burning, increasing speed and endurance, etc. Its becoming nearly impossible to keep up with all of them!
    Kathryn @ Dancing to Running recently posted…My Goals for Sunday’s St. Patrick’s Day DoubleMy Profile

  5. I have heard of the “fat burning zone” but I prefer a good HIIT workout to one where I have to keep going to reap similar benefits. It’s about exercising smarter not longer for me. Most days I barely want to get out there and go so a quick calorie and fat burning routine that helps me burn longer is always my choice. Great post!
    Stephanie recently posted…It’s National Chili Day!My Profile

    • That’s how I feel as well! I want to be done as quick as possible. The other day I heard this guy at the gym telling his friend he had been there for 2.5 hours…why?!? lol

  6. The description from Active is what I learned when studying to be a personal trainer. That said I still think steady state cardio is better than no cardio. I personally love walking because it’s low impact and helps regulate your hormones. :)
    Brittany recently posted…Tofu Veggie Noodle Bowl with Cabbage NoodlesMy Profile

  7. I’m all about HIIT…quick and effective! :)
    Annmarie recently posted…Wild Workout Wednesday: Ab Attack FinisherMy Profile

  8. I’m with you: I remember when fat burning zone was all the rage but thought that theory had been discounted. IMO HIIT has maximum bang for the buck.
    Marcia recently posted…Hip Opening Yoga for RunnersMy Profile

    • That’s what I thought too! Then the spin instructor said we’ll be saying in the fat burning zone and I was like wait what? lol

  9. I have heard of the fat burning zone but I never bought into it. I LOVE HIIT workouts because you get so much accomplished in so little time
    heather @ divas run for bling recently posted…5 Things to Consider When Choosing Your Next RaceMy Profile

  10. This is so interesting to me! I love HIIT BUT I don’t feel done at the end. I love a workout that makes me feel just completely DONE if that makes sense..I have heard of the fat burning zone, but not sure how I feel about it or my opinion without really researching and learning more specifics :)
    AJ @ NutriFitMama recently posted…Thinking Out Loud- How Kids Can Bring You Up & DownMy Profile

    • Agreed! I want to be totally beat by the end of my workout. The ones I’ve been doing that are strength with cardio thrown in (like burpees) definitely make me feel that way!

  11. It seems like it’s been a while since I’ve seen the term fat burning zone. The type of workout all depends on your goals so there isn’t any one BEST way to workout/train. Now I’m curious about the fat burning zone again :)
    jill conyers recently posted…Yoga, Food, Fitness and MotivationMy Profile

    • I agree there’s no best way! Sometimes long and steady is what you need (that’s me right now, with half marathon training) and other times HIIT will be the best way to reach your goals.

  12. I definitely prefer HIIT over long, extensive sweat sessions. My body physically cannot take an hour long class, so HIIT is perfect for me!
    Maureen recently posted…Things I’m Loving Thursday 2My Profile

  13. I wrote a post about this awhile ago as well ( the fat burning zone is such a huge misconception. I hate that it’s pointed out on all cardio equipment, because people seem to misunderstand what it means and how it applies to their goals. Just another one of my fitness pet peeves, lol!
    RFC recently posted…S.A.D.My Profile

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