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.





1 Comment

  1. Chris

    How do you define ‘Long Slow aerobic exercise’ ? Long and slow can also be intense even though it is not interval training.

    Long and slow doesn’t mean low intensity unless you are talking a slow mosy along a flat boardwalk.

    I’m 48 and I do endurance cycling. I do 200 kms a week of cycling and ride with guys in their 60s and 70s who are a true inspiration. They ride up steep hills much faster than I and regularly do 100kms rides. That is what endurance (so called long, slow?) exercise can do for you. If you think that they have smaller lungs and hearts, you would need to think again. I doubt anyone who does HIIT could match the levels of fitness these guys have, and every one of them is fit and has low body fat.

    You have to be clear that HIIT is an anaerobic activity and builds high twitch muscle and power – not fat so much. But endurance exercise builds low twitch muscle which is the type that go all day and burns fat; it cannot necessarily be called low intensity. I can guarantee you that riding 200kms a week up hills and on flats is anything but ‘unintense’.

    Dr Al has probably never actually done any endurance aerobics, which is why he would make such an ignorant comment as you say he has. Talk to athletes about these matters, not doctors.