A systematic review of 77 studies suggests that while both interval training and continuous moderate-intensity exercise are effective for fat loss, interval training may produce results in a more time-efficient manner. Researchers from Brazil and England conducted the review to identify what type of exercise—continuous moderate-intensity (MOD), high-intensity interval training (HIIT) or sprint interval training (SIT)—is best for weight loss.

The investigators defined MOD as continuous effort at 55%–70% of maximal heart rate. HIIT was defined as intermittent periods of training at 80% of HRmax, and sprint-interval training as intermittent training at an even greater, or “all-out,” effort. Participants were male and female, with mean ages ranging from 10 to 70 years, depending on the study. On the fitness scale, subjects included sedentary individuals all the way up to high-level athletes.

Data analysis showed that all training methods resulted in similar reductions in body fat (3.5%–4.6%), but typical MOD sessions lasted 38 minutes, while HIIT sessions were 28 minutes and SIT were 18 minutes. Authors of the review noted, however, that higher-intensity training may increase injury risk and cardiovascular stress and can present adherence challenges, since it’s less comfortable. Another difficulty in drawing conclusions from the review, according to its authors, is that training protocols varied widely regarding work-to-rest ratios and interval lengths, so no recommendations can be made regarding ideal interval training or MOD protocols.

The researchers recommend that future investigators improve methodological quality, sample size and assessment method to provide more compelling evidence pertaining to specific protocols. Look for the study in the British Journal of Sports Medicine (2019; doi:10.1136/bjsports-2018-099928).

Shirley Archer-Eichenberger, JD, MA

Shirley Archer, JD, MA, is an internationally acknowledged integrative health and mindfulness specialist, best-selling author of 16 fitness and wellness books translated into multiple languages and sold worldwide, award-winning health journalist, contributing editor to Fitness Journal, media spokesperson, and IDEA's 2008 Fitness Instructor of the Year. She's a 25-year industry veteran and former health and fitness educator at the Stanford Prevention Research Center, who has served on multiple industry committees and co-authored trade books and manuals for ACE, ACSM and YMCA of the USA. She has appeared on TV worldwide and was a featured trainer on America's Next Top Model.

3 Comments

  1. Diana Gordon on August 2, 2020 at 12:25 am

    Hi Kenny,

    How is it going?

  2. Joseph on August 5, 2020 at 10:34 am

    If you consider the physiology of each of these modes, one can understand why Interval training wins out. With the maximum intensithy of Intervals, you achieve a significant EPOC, thus significant longer after burner of metabolising fats. I remember as a 13 year old having my coach “encourage” me to run 24 x 400m repeats starting every 3 minutes as one of our daily workouts each week. Not only do you burn the fat faster, you improve your oxygen uptake faster with intervals. And remember, 5 calories of fat are oxidised for every litre of oxygen metabolised. One can check the studies on that as well. With that training I tied a national age group record for the mile my first race. I was sold on interval training. It bid me well in the national rowing programme later on as well.

  3. Eric Davis on August 5, 2020 at 3:21 pm

    I use to run a lot and this article might be the push I need to start again!! Very informative!!

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