Simplified Science #5: Shorten Your Workout to Lose Weight?

The modern paradigm of exercise for weight loss is long-distance jogging. But have you seen obsessive joggers? They look depleted. Their muscles look flat. This is partly because they are most likely in a catabolic (muscle wasting) state as opposed to an anabolic (muscle building) state. Most of our genes simply don't expect us to be jogging at a medium-intensity for a long period of time. Our genes expect us to either be walking for long periods of time or sprinting to catch/avoid becoming prey. Jogging, AKA chronic cardio, causes an excessive release of cortisol, our bodies main "stress" hormone. Excessive cortisol decreases anabolic growth hormones, causes blood sugar dysregulation and triggers fat storage.

In installment #4 of the Simplified Science series, we look at research published in the Medicine and science in sports and exercise journal showing that short duration, high intensity interval training is the most effective form of excercise for fat loss.

What is a HIIT workout:

HIIT exercise is a type of exercise that consists of short bursts of 90-100 percent output followed by adequate recovery time only to be followed with another short burst of 90-100 percent output followed by another set of adequate recovery time.

One HIIT workout may look like this:

- 20 seconds of burpees (90-100% energy output)

- 10 seconds recovery

- 20 seconds of burpees (90-100% energy output)

- 10 seconds recovery

- 20 seconds of burpees (90-100% energy output)

- 10 seconds of recovery

Repeat until you have completed a total of eight 20 second burpee sets and eight 10 second recovery sets

..... now on to the study

What Journal?:

Medicine and Science in Sports and Exercise


27 middle-aged women with metabolic syndrome who were between the ages of 45 and 60 with a BMI between 28 and 40 took part in the study to assess the impact of high intensity interval training (HIIT) on fat loss. The women took part in one of three "exercise programs" over the span of 16 weeks. The three exercise programs were: 1) no exercise, 2) low intensity training (walking), 3) high intensity interval training. Body weight and other biomarkers for metabloic syndrome were measured before and after the 16-week long study.


  • High intensity interval training significantly reduced waist circumference

  • The low intensity and no exercise groups did not have a significant impact on waist circumference

  • The HIIT group significantly reduced abdominal fat compared to the other groups (see chart here)

  • The HIIT group significantly reduced visceral fat (the hard, dangerous fat that surrounds your organs)

  • The HIIT group significantly reduced subcutaneous fat (the soft, grip-able fat that lies directly underneath the skin)

  • The HIIT group significantly reduced mid-thigh fat

  • The HIIT group reduced total body weight, BMI and total fat mass

  • Compared to the low intensity and no exercise groups, the HIIT group had the largest increase VO2 peak (VO2 peak is basically a measurement of how well your body uses oxygen during exercise. Increasing VO2 basically means increased performance during exercise)

The takeaway:

HIIT training is an effective way to lose body fat and improve various other health biomarkers. HIIT training can be as short as 4 minutes which could be benficial for anyone with limited time to exercise. This study calls into question the necessity of the current popular exercise model consisting of jogging for long periods of time at a moderate intensity.

Irving BA, Davis CK, Brock DW, et al. Effect of exercise training intensity on abdominal visceral fat and body composition. Medicine and science in sports and exercise. 2008;40(11):1863-1872. doi:10.1249/MSS.0b013e3181801d40.

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