Interval Training Better for Weight Loss Than Conventional Cardio

Dr. Al Sears. Sears—a medical doctor, nutritionist and leading thinker in the field of integrative health—believes everything we think we know about cardio is just about 100 percent incorrect.

Sears believes that the key to effective exercise for weight loss and overall health is not duration but intensity. He thinks the long slow constant speed aerobics that we’ve all been trained to believe is so good for us is exactly the wrong thing for us to be doing.

“After 30 years of working with extremely fit athletes, patients with failed, diseased or injured hearts and average people in between, one thing is apparent: doing continuous cardio exercise is a waste of time”, he says.

For many people in the exercise community those are fighting words. But Sears backs them up with some strong scientific arguments. “(Long slow constant cardio) just doesn’t build what your heart needs”, Sears says. “It doesn’t increase your heart’s ability to respond to real demands. In fact, for all your effort, you only reduce your ability to handle life’s stressful circumstances—the last thing you want!”

Sears points to the Harvard Health Professionals Study which followed over 7,000 people and found that the key to exercise is not length nor endurance but intensity. According to that highly regarded study, the more intense the exertion, the lower the risk of heart disease. “When you exercise for long periods at a low to medium intensity, you train your heart and lungs to get smaller in order to conserve energy and increase efficiency at low intensity”, says Sears. “Intensity is the key”.

Sears is one of the most outspoken critics of long slow aerobics, but he is hardly the only one. There has been quite  a lot of research in the last few years showing the clear advantage of interval training (which is by definition high intensity) over long slow aerobics, not only from the point of view of health measures (like VO2 max) but also in terms of fat loss.

And most exercise physiologists I talk to at conferences now believe that interval training is a far more effective for weight loss than an hour on the treadmill.

Sears himself has designed a terrific (and short!) interval training program that we recommend for the exercise portion of our own Diet Boot Camp program. It’s called PACE.

PACE stands for Progressively Accelerating Cardiopulmonary Exertion, but don’t let the long words scare you. It’s basically interval training, and from everything I hear from clients who are using it, it’s phenomenally effective.

Oh, and one more thing.. it only takes 12 minutes a day!

In his excellent book, “PACE: The 12-minute Fitness Revolution” Sears outlines three basic interval training programs and tells you how to customize them for your own needs. Here’s Basic PACE Workout number 1:

Warm-Up: 2 minutes


  • Exertion: 4 minutes
  • Recovery: X minutes


  • Exertion: 3 minutes
  • Recovery: X minutes


  • Exertion: 2 minutes
  • Recovery: X minutes


  • Exertion: 1 minute
  • Recovery: DONE

Note that this repeating pattern—exertion recovery—is at the core of every interval training program on the planet. The idea is you work really hard for a short period (in some programs only 30 seconds) then you do what’s called “active rest” or “recovery”—you’re still moving, but you work at a much lower intensity while your heart rate slows back down a bit. Then you do it all again.

The idea then is to alternate periods of hard exercise with periods of not-so-hard exercise. So for example, if you’re used to running at a “5” on the treadmill, for the “exertion” period you might run at a “7” for 30 seconds, then at a “4” (recovery) for a minute and a half. Then you’d repeat.

The reason the “Recovery” period is defined by X minutes in the PACE program is that how long you need to recover depends on your level of fitness.

In any interval program you can increase the intensity in a number of ways:

  1. You can increase the difficulty of  the “exertion period”, either by going longer (like 4 minutes in the PACE program) or working at a harder intensity (running at a “9” instead of a “7”)
  2. You can reduce the number of minutes between exertion periods (the “recovery” period
  3. You can increase the number of “sets” (exertion/ recovery)

In much the same way, you can make the program easier by extending the recovery period or making the exertion period less of an exertion (running at a “6” instead of a “7”, etc.)

I’ve been recommending interval training for a long time. You can do intervals walking, running, swimming, jumping rope or using machines.

Try it on for size and see what you think. And once you do, I’d love to hear what you thought about it.

This kind of training is a way more effective (and streamlined) way to work out, and, coupled with strength training, will give you far better results in far less time than conventional long, slow aerobics.



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  • Brenda

    Even though I realize that this information is correct…….. I must admit I still have trouble letting go of the idea that my Jazzercise classes were bad for me. I mean people have been dancing as a part of life since the beginning of time. When the article above said “long slow constant speed aerobics” what does that mean really ? How slow is slow and how long is constant? I can understand why long jogs would be bad but what about a long walk or even a short walk? What about dancing in a Jazzercise class for 35-40 minutes? That isn’t exactly long but it is constant? I also know that there isn’t enough strength training going on in Jazzercise………but I am a little confused about the cardio strengthening part. I will be buying the book recommended here.

    I see more and more info coming out about this type of exercise and how aerobics wasn’t so good. I sometime wish I was born 20 years later so I could have not suffered from misinformation about diet and exercise. At least my kids can benefit from past mistakes.

    • Meredith

      Jazzercise has evolved over the years to incorporate all these fitness trends. So yes it does have strength and HIIT. Their new Fusion classes do just that. Here is it defined: Jazzercise Fusion — fuse cardio with strength training for maximum fat burn in this circuit-based high intensity interval training class

  • tammy

    I heard about this and started it several months back. I do a 2 min. warm up and then the 30 secs/90secs and I work out on the mini trampoline. It is a fast and easy workout and it has incredible results.

  • Brenda I’ve read Dr. Sears book and think I can shed a bit of light.

    Firstly, the cardio he refers to is akin to going on a treadmill for 50 minutes at ‘5’. Over many months of this type of training the body will actually adapt such that it becomes more efficient at performing steady state cardio. There are a few reasons why this type of training has some negative effects – as explained in the book, and referred to in Johnny’s article.

    The long and the short of it is that more intense exercise has a lot of benefits – keep in mind ‘intense’ for one person maybe different than another. The book recommends recognizing your starting fitness level and working from there.

    Circling back, your jazzercise isn’t exactly what he is referring too, and I believe you are still getting health benefits. Likely you are varying your moves and your heart rate is fluctuating here and there. Perhaps not the ‘best’ exercise but certainly has it’s benefits. Maybe you could consider adding in or swapping in a couple days of circuit style training with weights or perhaps doing some cardio the way Johnny mentioned above with sets of intense exercise mixed with brief rest periods.

    The overall message, which is actually very nice, is that we don’t necessarily need to spend a lot of time on exercise, in fact less is more – if done right!

  • johnny quick

    Great article Jonny!

    Recent interval training research from Mc Master University in Hamilton, Ontario, Canada revealed that subjects performing 4-6 thirty second sprints on a stationary bike with 4 minutes rest between sprints improved as much or more than controls doing two to three hours on a stationary bike at a comfortable pace.

    In other words, two minutes of sprints equaled two hours at a comfortable pace.

  • Andrew

    I think intervals are great, but I’ve heard of plenty of studies about the benefits of walking. Now whether that is down to fresh air, the outdoors, a brake from routine, it is hard to be sure.

    But interesting you say the heart can get smaller to adapt to that type of training. Is that smaller than a person doing no exercise. Or smaller than a person doing higher intensity, it’s an important distinction. I don’t think it should be a problem if you do both types (as I do) – heart will still be strong to cope with intensity side.

  • Alan

    In my previous studies, I had come to believe that the body uses primarily fat as its fuel source during low intensity activity such as sitting around and walking, and gradually shifts toward using primarily carbohydrates as the intensity increases.

    If this is true, it means the real key to fat loss is to increase your basal metabolic rate by increasing lean muscle mass and supplementing with walking as much as possible to burn additional fat calories.

    High intensity aerobics would accomplish neither of these very well, as they are not loaded enough to build muscle and too fast to burn fat over carbohydrates. So, is my premise incorrect? Does the body not favor carbs over fat during high intensity activity and vice versa during low intensity or no intensity activity?


  • Dr Dave

    Brenda, you may not have been too far off the mark with your jazzercise program. The key objective of interval training or HIIT workouts is to work at a high enough intensity for a period of time to push your cardiovascular system toward its theoretical maximum output. Because working close to your theoretical max can’t be physically sustained for long, these high intensity bursts must be broken up with recovery periods of lower intensity. One of the best ways to guage your intensity level is by monitoring your heart rate during some of the more physically demanding portions of your Jazzercise routine. If you are pushing into the 85% to 90+% of your theoretical HRmax (220 – your age) zone, you are already doing some high intensity workouts. If your just falling a bit short of this target range, maybe you can pick up the beat a little or find other ways to make it more demanding – such as using wrist or ankle weights. Due to the higher energy demands of HIIT, the rest intervals are essential for recovery before the next bout. But thats okay, because your body gets more physiological bang for the buck (1 minute of vigorous 7-8/10 exercise = 2 minutes of moderate 5-6/10 exercise) so the theory goes, you won’t need to put as much time into each workout. One caution though, there is a high risk of injury with this type of workout – especially amongst people with physical limitations or health problems. Also, because it doesn’t really address the endurance side of the fitness equation, one could argue there is still a need to incorporate some continuous longer duration moderate to vigorous intensity workouts into your routine. Hope that hepls!

  • David

    I totally agree with interval training for heart health. I avoided a triple bypass by doing interval training on my exercise bike 3 times a week and changing my diet to low carb. It really works- I also lost weight!

  • Mom of 5

    I have been struggling with exercise routines for years. I recently heard about interval training and decided to give it a try today. I used my elliptical and set it for 30 minutes. I am quite overweight so for now I started doing the intensity for 1 minute, pushing my body as hard as I could without flying off of the machine, and then the cool down for 3 minutes or as long as it took sometimes 3 1/2. I am usually to the point of tears just watching my timer waiting for my 30 minutes to be up, but not today. Not only did it seem fairly easy to make it through the time, but I now feel like I have energy for the rest of the day, where as I usually want a nap. I know it is only my first day so I cannot attest to any “success” but I will say this, I have never sweat so much in my entire life! And it is a good sweat that almost feels like a sense of accomplishment. I will be back in a month to post some real results!

    • Cheryl C

      Mom of 5 – I was you 3 months ago. I have kept it up. I feel great. It’s hard to really commit to reaching the intensity level you need, but you can do it! I know what you mean about the sweat. It just pours off you, and you can barely breathe. If you are not using a heart rate monitor, i recommend it. at age 50 (BMI 24.8), I now do my intervals as “ramp up” for one minute ’til I achieve 155 HR, hold for a minute, and rest (by slowly cycling or walking on the elliptical) for 2 minutes. My heart rate returns to 125 in about 50 seconds. I do that 10 times. On the first 3 intervals, I don’t reach 155. I build up…. 140 for the first, 145 for the second, and 150 for the third.

      By having the heart rate monitor, I can tell exactly how much recovery time I need. And, even though I recover (down 30 beats per minute) at 50 seconds, I still rest for 2 minutes, which gets me down to 111.

      By measuring the heart rate throughout, I can tell how I am improving over time.

      And, yes, I am losing that menopausal belly fat — the stubborn stuff last to go.

  • […] Interval Training Better for Weight Loss Than … – Great article Jonny! Recent interval training research from Mc Master University in Hamilton, Ontario, Canada revealed that subjects performing 4-6 thirty second …… […]

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