June 12, 2013
“Abs are made in the kitchen, not the gym”
True – but we can still use exercise to speed up the process. The role physical activity plays in your weight loss journey is almost exclusively calorie based. Therefore it hardly matters what the actual method of cardio is (ie. running, boxing, spinning, dancing), but rather the technique behind the sport deserves most attention.
Before I continue, it is important to note that there are credible experts and studies that support opposing views on this matter, but I will present some of the latest research, and my interpretation of their data.
So what type of cardio should you do to make the greatest impact on your progress?
For simplicity let’s divide the types of cardio into the two main categories: low-intensity steady-state cardio (LISS) and high-intensity interval training (HIIT). We ideally would want to examine the effects of each short term (during and immediately following exercise), post-exercise (24-48 hours), and also long-term (weeks to months).
Low-Intensity Steady-State Cardio vs. High-Intensity Interval Training
The main argument in favor of the LISS cardio zone is based on the notion that keeping your heart rate lower is associated with a higher proportion of fat loss, during exercise.
Achten & Jeukendrup conducted one of the best designed trials to support this, as they showed that peak fat oxidation occurred at 63% of max heart rate (VO2 max). As the heart rate increased, fat oxidation progressively declined to a minimal point at 82% VO2 max .
It turns out that while LISS does indeed target higher amounts of fat during exercise, the following 3-6 hour period tells us a different story.
Phelain and his team showed that while low-intensity training did have a higher fat-oxidation during exercise, it was statistically insignificant. Moreover, the higher intensity group saw substantially higher fat oxidation at the end of the 3-hour recovery period !
In Terms of Calories…
Well you don’t really need someone to demonstrate in a lab that moving harder is going to burn more calories do ya?
When we start to study the longer-term effects of cardio on fat burn, a completely different picture is painted. Two well-designed studies examined net fat oxidation at the 24-hour mark in both low-intensity and high-intensity groups, and found no differences [3, 4]. In other words, after a full day has gone by, we see no differences in total fat burn from cardio.
In Terms of Calories…
A very well-known study by LaForgia and his crew, among many others these days, show clearly that Post-Exercise Oxygen Consumption (EPOC) is significantly greater in the HIIT group (vs. LISS), 3-24 hours after the exercise . What this study shows in simple English is that the higher our heart rate gets during cardio, the more calories we will burn afterwards, throughout the day.
Some experts, Lyle Mcdonald for one, will argue that the amount of extra caloric burn we get is not substantial enough to be important . I personally disagree… with the caveat that it really depends on your program and where you are with your fat loss needs.
Long-Term Research Provides Clear Answers
A 15-week study conducted by Trapp shows significantly higher reductions in subcutaneous (stubborn) body fat in the high-intensity group, when compared to the low-intensity group . A similar outcome was produced in Tremblay’s 24-week study, where the high-intensity group lost substantially more subcutaneous fat .
There are other arguments in support of steady-state cardio that deal with criteria different from weight loss. The mainstream argument for use of LISS to lose weight is from claims that fat oxidation is greater.
We can clearly see that fat oxidation is not significantly different between the different forms of cardio – contrary to what most people would have you believe.
When looking to lose weight, you want to choose the type of cardio that will induce the greatest calorie burn, since we know that a calorie deficit must be present for fat loss to occur. The studies clearly indicate that more calories are consumed through HIIT in the short-term and post-exercise window.
The data surrounding the bigger long-term picture shows over and over again (I only posted a mere couple of examples), that a program incorporating HIIT is going to help someone lose body fat significantly quicker than someone on a LISS regimen, or someone inactive.
The main reasons for this, which is not thoroughly explained in this article, but perhaps a future one:
- EPOC is greater in the HIIT group
- HIIT raises the capacity for fat oxidation by causing the body to adapt to extreme stress
- HIIT is actually shown to decrease post-exercise appetite
- HIIT combined with resistance training shows greater muscle gains and/or retention
- LISS is associated with increased muscle depletion
So there you have it. The data clearly shows us that lifting harder, sweating more, breathing heavier, sprinting until you vomit, and etc… is associated with substantially greater weight loss. Shocking!
Next time you run – RUN HARD!
- Achten J, Jeukendrup AE. Relation between plasma lactate concentration and fat oxidation rates over a wide range of exercise intensities. Int J Sports Med. 2004 Jan;25(1):32-7.
- Phelain JF, et al. Postexercise energy expenditure and substrate oxidation in young women resulting from exercise bouts of different intensity.J Am Coll Nutr. 1997 Apr;16(2):140-6.
- Melanson EL, et al. Effect of exercise intensity on 24-h energy expenditure and nutrient oxidation. J Appl Physiol. 2002 Mar;92(3):1045-52.
- Saris WH, Schrauwen P. Substrate oxidation differences between high- and low-intensity exercise are compensated over 24 hours in obese men. Int J Obes Relat Metab Disord. June; 28 (6): 759-65.
- LaForgia J et. al. Effects of exercise intensity and duration on the excess post-exercise oxygen consumption. J Sports Sci. 2006 Dec;24(12):1247-64.
- McDonald, Lyle. http://www.bodyrecomposition.com/research-review/research-review-effects-of-exercise-intensity-and-duration-on-the-excess-post-exercise-oxygen-consumption.html
- Trapp EG, et al. The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women. Int J Obes (Lond). 2008 Apr;32(4):684-91
- Tremblay, et al. Impact of exercise intensity on body fatness and skeletal muscle metabolism. Metabolism. 1994 Jul;43(7):814-8.