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Interval Training Beats Continuous Exercise to Burn Fat (Journal of the American Medical Association) recently reported that, “there’s no consensus on the best exercise approach to burning fat, which is preferred over losing muscle for shedding weight.”

However, some evidence, according to JAMA, “suggests that interval training–including high-intensity interval training (HIIT) and sprint interval training (SIT) — can help people reduce body fat and lose weight more than sustained moderate exercise, even if the exercise burns fewer calories.”

That conclusion is based, in part, on evidence that interval training increases post exercise resting energy expenditure – via a mechanism known as excess post oxygen consumption (EPOC), which may last up to 24 hours – depending on the intensity of the interval training.

JAMA sites the systematic review and meta-analysis (multiple similar studies) in the British Medical Journal (BMJ) of Sports Medicine, which concluded that, “interval training and MOD (moderate-intensity, continuous training) both reduce body fat percentage. Interval training provided 28.5% greater reductions in total absolute fat mass than MOD.”

Research – Is Interval Training the Magic Bullet for Fat Loss? A Systematic Review and Meta-Analysis Comparing Moderate-Intensity Continuous Training with High-Intensity Interval Training – from Brazil and the United Kingdom, states that MOD reflects an intensity of 55 to 70 percent of maximal heart rate (220-age), while HIIT or SIT represent an “all out” intensity – with different recovery intervals.

Using 41 qualitative and 36 meta-analyses, the results demonstrated that during a 12-week supervised training period – walking/running/jogging – with individuals less than thirty years of age, both interval training and moderate-intensity continuous training d similar benefits for body fat percentage reduction. However, interval training provided greater reductions in total absolute fat mass.

In 1998, when I was an associate professor in the School of Public Health and Preventive Medicine, Louisiana State Medical Center, I participated in a funded, third party study to evaluate the effectiveness of my Sports Performance Training System – a six week, comprehensive program – combining four days per week of interval sprints (HIIT & SIT), weight and core training, flexibility, meal plans, and nutritional supplements.

The subjects (20) consisted of a diverse group of individuals – seven females and fourteen males – 16 to 50 years of age. The parameters tested before and after the six-week training included: maximum oxygen consumption (VO2 max), oxygen consumption and heart rate at anaerobic threshold (AT), resting (RHR) and maximum heart rate (MHR), total body fat, and lean weight, along with anaerobic power and capacity.

It’s important to note that no continuous, moderate intensity exercise – running, biking, or swimming – was utilized by the participants during the study period. Nevertheless, the aerobic metabolism (VO2max) improved by an astounding 31% – with a concurrent improvement of the anaerobic threshold of 13%. The resting heart rate decreased on average by 10 beats per minute – with the anaerobic power and capacity improving by 16.7% and 17.3%, respectively.

On average, lean muscle mass increased by 9.4 pounds, while body fat decreased by 5.78 pounds. The results of this study later became part of my book – Lean & Hard – the body you always wanted in 24 workouts (4 workout per week over 6 weeks). It was quite evident that an individual could forgo the extended time of a moderate intensity exercise session by increasing the intensity of the interval workout.

It was an inverse relationship – lower intensity and longer duration versus a higher intensity with shorter duration – giving those time constrained individuals or those that preferred lower intensity training – options for a similar outcome, as the BMJ study has also confirmed.

No matter which option you choose, it’s important to have a medical clearance by your primary care provider before you start to offset the potential risk that unfamiliar or new exercise at any intensity provides – especially for those joining or re-joining the exercise club.

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