“Want to lose that annoying belly fat? Run!” I’m sure everyone has heard it for years. Hit the track or treadmill and churn out those miles, but recent studies have shown that this may not be the best idea. High Intensity-Interval Training (HIIT) has been around the body building community for a while because it provides a quick effective way to burn unwanted calories and fat. Now, HIIT is leaking into the mainstream and starting to challenge Continuous Aerobic Training (CAT) to become the “best cardio for fat loss”. So when it comes to burning fat, should you stick to CAT or follow the new trend and switch to HIIT.
In this scenario, the null hypothesis would be that HIIT training doesn’t affect fat loss any differently than CAT training. To reject the null substantial evidence would have to be presented in this area.
Elisabeth Sherratt MS. RN. wrote an article discussing the best way to burn fat. In her article, Sherratt discussed the pros and cons of each workout. When it comes to CAT, you need to change up your exercises according to a 2006 study done by National Runners Health Study. 8080 male runners were tracked over 9 years and the results showed that the overwhelming majority of the runners gained fat and waist circumference. Now, some of that was due to age and runners failing to continuing their running, but the runners who actually increased their milage over time gained little to no fat. Sherratt says you would need to increase your running total by “3 times each week” to maintain your body fat and even lose it.
HIIT has also been proven to increase calorie burn even AFTER a workout. Sherratt sites studies that state “HIIT offers the metabolic benefit of excess post exercise oxygen consumption (EPOC). After HIIT exercise, oxygen consumption (and therefore calorie expenditure) remains elevated, as the working muscle cells restore to their pre-exercise physiological and metabolic baseline. Calorie burning continues after exercise has stopped translating into a greater total calorie burn.” So when doing HIIT training, you can burn calories even after your workout, which is similar to the way weight training works. These findings were backed in another article of meta-analysis done by Micah Zuhl, and Len Kravitz. They found that HIIT workouts also burn calories after the workout is finished as well: “Another metabolic benefit of HIIT is excess postexercise oxygen consumption (EPOC). After an exercise session, oxygen consumption (and thus caloric expenditure) remains elevated as the working muscle cells restore physiological and metabolic factors in the cell to pre-exercise levels. This translates into higher and longer calorie burning after exercise has stopped.” So basically, if your looking to keep burning calories after you workout, try HIIT training over CAT training.
The last key aspect Sherratt discusses is burning of visceral fat, often times found around the belly. “Hottenrott, Ludyga, and Schulze (2012) tested recreational runners, for 12 weeks. One group run 2.5 hours of long distance running compared to a group that ran four 30-minute interval workouts per week. After 12 weeks, the BMI of both groups was nearly the same; however, the sprinters lost more belly fat, a decrease of 16.5% with no fat free mass loss, meaning they preserved their muscle. The long distance group lost 6.5 % of their belly fat and a considerable amount of muscle.” So, according to this study if you want to burn belly fat go with HIIT. Another article backed this finding and even went a step further in talking about fat loss in general. Micah Zuhl, MS and Len Kravitz PhD examined the affects of both HIIT and CAT training, but found one key difference in their meta-analysis. It seems that HIIT training is in fact better for burning fat. “Increasing mitochondrial density can be considered a skeletal-muscle and metabolic adaptation. One focal point of interest for metabolic adaptations is the metabolism of fat for fuel during exercise. Because of the nature of high-intensity exercise, its effectiveness for burning fat has been closely examined. Perry et al. (2008) showed that fat oxidation, or fat burning, was significantly higher and carbohydrate oxidation (burning) significantly lower after 6 weeks of interval training.” If you want to burn fat, and burn it fast, start HIIT training and drop CAT training.
What did I find in my examination of training? If you want to burn fat, try out HIIT training. Listen, it may not be for everyone, but I feel that after the overwhelming evidence points to the benefits of HIIT training over CAT training. There is enough evidence here to reject the null hypothesis and go with HIIT training over CAT training when it comes to fat loss. The meta-analysis could suffer from the file drawer problem, because studies that show that both exercises work equally may not be published, but I feel there is still enough evidence to prove this. I personally have been working to lose weight for 4 months now and have been doing CAT training along with my weight training exercises, my research produces enough evidence for me to switch over to HIIT training, what about you?