The Great Debate: High-Intensity VS Moderate Cardio For Fat Loss

A while back I wrote a blog about which one was better for fat loss between cardio and strength training. I concluded that both were equally important and effective, just in different ways.

So a few people reached out and asked me which was more effective for fat loss between high intensity and traditional cardio but instead of giving you my opinion I thought I’d tell you what the research says.

When it comes to fat loss, cardio is often a go-to for many individuals looking to shed some extra pounds. But with so many different types of cardio out there, it can be difficult to know which one is the most effective for fat loss. Two common types of cardio are high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT). In this blog, we'll take a look at some recent studies to help determine which one is more effective for fat loss.

What does the research say about high intensity for fat loss?

One study published in the British Journal of Sports Medicine in 2017 found that both high intensity interval training (HIIT) and moderate intensity continuous training (MICT) led to a reduction in body fat percentage, with no significant difference between the two groups. However, HIIT was found to be more effective at reducing total body fat mass.

The study suggests that HIIT may be a more efficient form of cardio for reducing body fat mass in overweight and obese individuals. 

Additionally, the study found that both HIIT and MICT had similar effects on lean body mass, suggesting that neither form of cardio was superior in preserving muscle mass during weight loss (Wewege et al, 2017).

In another systematic review and meta-analysis published in the Journal of Obesity in 2017 compared the effects of HIIT and MICT on body composition changes. The study found that both HIIT and MICT led to significant reductions in body fat percentage, with no significant difference between the two groups (Steele et al, 2017).

The study also found that HIIT was associated with a greater reduction in waist circumference, a marker of abdominal fat, compared to MICT. This suggests that HIIT may be more effective at targeting abdominal fat, which is often associated with increased health risks.

And finally, a systematic review and meta-analysis published in the Journal of Cardiopulmonary Rehabilitation and Prevention in 2018 compared the effects of HIIT and MICT on vascular function. The study found that both HIIT and MICT led to significant improvements in vascular function, with no significant difference between the two groups (Ramos et al, 2015).

The study suggests that both HIIT and MICT are effective at improving vascular function, which is important for cardiovascular health.

Which one is better: High-intensity or traditional cardio?

Well it seems neither are superior to the other from a metabolic standpoint, however as far fat loss is concerned, high intensity may have a slight advantage in its ability to create the same results in a shorter time frame.

According to various studies, both moderate intensity and high intensity seem to result in fat loss. The better question is “which one is better for you?” in which case, in order to answer that question you’d have to consider which ones you prefer and which ones you can sustainably do.

One of the benefits to high-intensity is that you can still get the same energy expenditure due to the “afterburn” also known as “excess post exercise oxygen consumption” where the body continues to “burn” energy even after the training session has ended.

How to create an “after burn” effect

It’s important to note that participating in a high-intensity workout class does not guarantee that you'll achieve the afterburn effect.

In fact, to truly experience this increased calorie burn, it's crucial that an athlete pushes themselves to reach 80-90% of their maximum heart rate during their workout.

Simply attending a class labeled as 'high intensity' does not inherently ensure this level of exertion; the key is the actual physiological response elicited in the individual, which means actively monitoring and striving to reach these higher heart rate zones

Gaining weight with high intensity workouts?

Athletes can sometimes become disproportionately hungry to their energy expenditure resulting in weight gain.

Unfortunately this is often a challenge among some athletes and often the issue lies in the fact that they become disproportionately hungrier following a high intensity exercise. Its important to note that although HIIT is effective in fat loss, it is also extremely draining which often results in athletes overeating, and by default putting them back into an energy surplus.

As with most things…. Nothing is as straight forward as it seems. Remember the mars bar theory? You know the one that claims you have to run for 30 minutes in order to “burn” off a Mars bar? Unfortunately that is an oversimplification of energy balance. Energy balance is a complex subject but it doesn’t mean you have to understand everything to see results.

Having a basic understanding of the energy availability in food can  help you gauge how much to consume vs how much to use.

Takeaways

Both HIIT and MICT are effective at reducing body fat percentage, with no significant difference between the two groups. However, HIIT may be more effective at reducing total body fat mass and targeting abdominal fat. Additionally, both forms of cardio are effective at improving vascular function, which is important for overall health.

Ultimately, the best form of cardio for fat loss may depend on individual preferences and goals. Some individuals may prefer the shorter, more intense workouts associated with HIIT, while others may prefer the longer, steady-state workouts associated with MICT. It's important to find a form of cardio that you enjoy and can stick to in order to achieve the best results.

Resources

Wewege, M., van den Berg, R., Ward, R. E., and Keech, A. (2017) The effects of high-intensity interval training vs. moderate-intensity continuous training on body composition in overweight and obese adults: a systematic review and meta-analysis. Obesity Reviews, 18: 635– 646. doi: 10.1111/obr.12532.

Steele J, Plotkin D, Van Every D, Rosa A, Zambrano H, Mendelovits B, Carrasquillo-Mercado M, Grgic J, Schoenfeld BJ. Slow and Steady, or Hard and Fast? A Systematic Review and Meta-Analysis of Studies Comparing Body Composition Changes between Interval Training and Moderate Intensity Continuous Training. Sports (Basel). 2021 Nov 18;9(11):155. doi: 10.3390/sports9110155. PMID: 34822354; PMCID: PMC8619923.

Ramos JS, Dalleck LC, Tjonna AE, Beetham KS, Coombes JS. The impact of high-intensity interval training versus moderate-intensity continuous training on vascular function: a systematic review and meta-analysis. Sports Med. 2015 May;45(5):679-92. doi: 10.1007/s40279-015-0321-z. PMID: 25771785.