Q: Which is more effective for fat loss – 20 min of high intensity interval training or 60 min of cardio in the fat burning zone?


The short answer is that the 20 minutes of higher intensity intervals would probably do more for fat loss in the long run than the 60 minutes of low intensity cardio. But I’m not one for short, easy answers, because you will never truly understand the complicated fat loss process, and thus you will never learn how to separate fact from myth, efficient plans from inefficient ones. Trust me, its worth educating yourself a little bit if you truly care about getting real results.

Changing your body/losing fat is not just about how many calories you burn while exercising, or what percentage of those calories come from fat as a fuel source. Its about the positive effects exercise can have on (1) your resting metabolic rate (Technically, this is your truest “fat burning zone”, as the body burns predominantly fatty acids at rest, or in other words, the greatest percentage of fat as a contributing fuel source occurs under resting conditions, not exercising ones) (2) muscle building/fat burning hormonal release — the true key to physical change. High intensity intervals has a more dramatic effect on these processes than low intensity cardio, but there is another MODE of exercise that has a greater effect than both combined. Thus there is a more efficient way to go about your fat loss business. What if you tried 40 minutes of STRENGTH TRAINING?

Compared to strength training, cardio (any form of cardio) is inferior for body composition change. Strength training is not just for meatheads trying to get huge, its also the most efficient way to get your body to burn fat — AT REST. How? Strength training causes microscopic damage in the muscle cell. The repair process can take up to 72 hours to complete. And all of the cellular processes that happen during this phase require energy = CALORIES. And since all of this happens at rest, a large percentage of those calories will come from fat. So even though you may burn more calories during an hour of low intensity cardio or 20 minutes of intervals than an hour of strength training, you will burn more calories in the 71 hours that follow after a strength training session. Which do you think has the biggest impact on your goals?

And yes, intervals will give you a nice fat burning growth hormone surge/release, but so does strength training if you do it right. And the strength training has a much more profound, sustained metabolic effect in the recovery period — as described above. Fat burning hormone release, elevated met rate, and the opportunities to wear spandex, grunt really loud, and wear sunglasses inside the gym, you can’t beat that (I hope you know I’m kidding).

So curls are good for the girls, and also good for the guys trying to get the girls.

If you enjoy the science, here is a little more about what goes on in response to a strength training session:

  1. Satellite cells are activated when muscle fibers receive trauma or damage.
  2. Satellite cells fuse to existing muscle fibers and help to
    repair/regenerate the damage by increasing the size and number of
    contractile proteins (called actin & myosin) within those fibers.
  3. The body restores cell fluids, electrolytes, and minerals lost during training.
  4. The body must refill muscle glycogen stores as glycogen is the
    primary fuel used during high intensity training.
  5. The immune system responds with a sequence of actions leading to
    inflammation. This inflammation is what causes muscle soreness. The
    purpose of this inflammation is to contain the damage within the muscle
    cells, increase blood flow and nutrient delivery to the damaged area,
    repair the damage, and clean up the injured area of waste products.
  6. Antioxidants scavenge free radicals and repair oxidative stress
    caused by the increased rate of oxygen consumption during the training
  7. Growth factors (such as IGF-1) regulate insulin metabolism and stimulate protein synthesis.
  8. Testosterone, cortisol, and growth hormone levels rise, fall, and
    return to baseline levels in their own respective patterns (assuming you
    are training naturally without performance enhancing drugs).
  9. All of the above processes can take up to 48-72 hours under normal
    circumstances but can be delayed by many factors including poor dietary
    decisions, lack of sleep, and high stress levels just to name a few.
  10. All of the above actions require energy (calories).
    This is why we say that strength training boosts the metabolism (the
    rate at which your body burns calories on a daily basis) and is so
    crucial to the body composition change process.

If you still don’t believe me, and would rather hit the treadmill instead of the dumbbells, despite everything I’ve just taught you, there may be nothing I can do for you. But I wish you luck nonetheless.