Are you performing cardio to lose fat? Yes. Then a brand-new meta-analysis (a review of all of the studies on a topic) comparing High Intensity Interval Training (HIIT) and more traditional cardio, referred to as Mild Intensity Continuous Training (MICT) and their effect on fat loss will guide your exercise decisions. Dr. James Steele, a brilliant young exercise physiologist and statistician in the UK (featured on the Discover Strength Podcast here), examined 54 randomized control trials comparing interval to traditional cardio to determine which was more effective for fat loss. These studies included men and women, a variety of ages, and normal weight, overweight, and obese subjects. It’s fair to say that this is the most comprehensive meta-analysis ever conducted on the effects of intensity of effort during exercise on changes in measures of fat mass and one of the most interesting studies in the field of exercise published in years… And it should change what so many of us believe about cardio.
- It has been speculated that interval training confers superior fat loss benefits compared to “normal” cardio and this is purportedly caused by EPOC (excess post-exercise Oxygen Consumption) also known as the after burn of interval training. The researchers concluded that this after burn is negligible and stated, “Additional energy (calorie) expenditure attributed to EPOC during interval training is modest and thus unlikely of practical meaningfulness from a fat loss standpoint.”
- Effort or intensity of cardio (interval versus traditional) makes very little difference in changes in fat loss; thus, individuals can choose whichever they prefer: Interval style training (which is often more time efficient) or traditional cardio training.
- Most importantly, neither interval training or traditional cardio burned significant number of calories or resulted in fat loss. The authors concluded, “The amount of exercise required to achieve practically meaningful changes in this outcome seems to be unrealistic for most individuals. It is much easier to create an energy deficit from dietary restriction, which, therefore, should be the focus of weight loss interventions”
Important note: Most people use cardio for fat loss and this comprehensive study concluded that this is ineffective (interval or traditional) however, it should be noted that interval and traditional cardio IS important and purposeful for improving cardiovascular function and mitigating cardiovascular disease risk (hence, the name, cardio). Although our Pelotons, group interval training classes, and my beloved Stairmaster Stepmill play no role in fat loss, they are good for our hearts. Cardio IS good, it just doesn’t do what most people use it for.