by Tom Venuto
Have you ever heard this: "If you do cardio workouts hard enough (with enough 'intensity') - using interval training (short bursts of hard work), you can burn a ridiculously huge amount of fat in just minutes! A 10-minute high intensity interval cardio session, or even 7-minutes, or yes, even 4-minutes (Tabata), will burn fat like crazy!"
Perhaps a trainer told you something like this, or you read it in a fitness book, magazine or website. If you haven't heard this, then rest assured, thousands of others have. High intensity interval training, aka "HIIT", has been promoted heavily for years, and often by well-known, well-credentialed trainers and PhD scientists.
The problem is, most of the claims about HIIT are, at best, a misunderstanding of what the science on HIIT actually says, and at worst, total B.S. A new study was published this year (2019) which uncovered everything exercise scientists know so far about interval training, specifically as it applies to fat loss (41 individual studies reviewed). I've summarized the findings here for all our readers. Take a look.
1. The new British Journal of Sports Medicine study on interval training and fat loss found that both types of cardio (steady and interval) are effective for fat loss and both reduced body fat percentage in similar amounts. However, the interval workouts were shorter, so promoted more fat loss per unit of time invested.
2. Interval training may be slightly more effective for fat loss, depending on how the program is designed, but it's not a magic bullet for fat loss. Interval training may, however, be a legitimate magic bullet for time efficiency, especially for fitness and health benefits. In just minutes, you really can get cardiovascular improvements.
3. Cardio, whether steady state or interval training, will not help with fat loss at all if nutrition is not controlled and adherence to the program is not consistent. (Read that one again!)
4.The interval training appeared slightly more effective overall for reducing total absolute fat mass (in lbs), but the amount of fat loss was not large and neither was the difference between the interval and steady state groups.
5. There is still no consensus about whether a single type of interval workout is the best for fat loss. There are many different interval protocols that can work. However, there are some general guidelines that must be followed or fat loss will be minimal, even with intervals.
6. Much of the previous research on interval training studied fitness and health benefits and didn't even measure fat loss. Many people, including respected trainers, are mixing up interval training for fat loss versus interval training for health and fitness benefits (they are not the same thing). Unfortunately, you don't burn diddly squat body fat with just a few minutes of intervals, no matter how intense they are.
7. Super short interval workouts can increase cardiovascular fitness and health, but the duration of interval training was a major factor that influenced decreases in body fat. The length of high intensity interval training (HIIT) protocols that resulted in the most significant fat loss was 28 minutes on average (compared to 38 minutes for steady state cardio).
8. Supervised training was associated with increased fat loss, which suggests many people doing interval training on their own have not been reaching the intensity thresholds needed to optimize results.
9. Jogging and running were forms of exercise that favorably influenced fat loss in interval training programs, but more than a few short sessions of running per week can interfere with strength and muscle gains when done concurrently every week with intense weight training, especially in the legs. No impact exercises like cycling, are more forgiving on leg muscle retention.
10. In sum, this study confirms that high intensity interval training (HIIT) and sprint interval training (SIT) is more time-efficient than lower intensity steady state cardio.
I hope you found this enlightening and it helped clear up some of the confusion about intervals and fat loss.
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