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Do HIIT Workouts Burn Fat? (3 Reasons Why It's Effective)

Connor Sellers
Published by Connor Sellers
Fact checked by Donald Christman, BHSc FACT CHECKED
Last updated: September 13, 2022

Not all workouts are created equal. Some build you up slowly, and others give you quick progress.

High-intensity interval training, popularly known as HIIT, has become quite popular over the years for its dynamic movements, short workout time, and quick results.

In more than ten years as a physical trainer, I’ve constantly recommended HIIT cardio to many clients, and they’ve rarely failed to deliver results. Yet, I come across many who are skeptical of high-intensity workouts.

So, in this article, I’ll share my experiences and observation of how and why HIIT exercise helps you lose weight.

Quick Summary

  • High-intensity interval training has become a popular form of exercise because it requires zero or minimal equipment and can be done at home.
  • HIIT training is an excellent way to burn fat, build muscle, and improve cardiovascular endurance.
  • Since HIIT can be very intense, choosing a workout will depend upon your current fitness levels, age, and other factors.

How Does HIIT Burn Fat?

Close up shot of sweaty buff person

HIIT burns fat through the afterburner effect. The afterburner effect refers to the increased number of calories your body burns after high-intensity exercises.

With normal cardio exercises, you’re burning calories during and a little while after working out.

With HIIT, it’s more intense. Studies have shown that a HIIT session increases your metabolic rate for hours after exercising [1].

Other studies show that high-intensity exercise can increase your metabolism after working out more effectively than regular aerobic training or strength training [2].

Even though HIIT sessions are short, they are known to produce more health benefits than moderate-intensity exercise [3] [4].

Like traditional exercise, HIIT can decrease body fat and waist circumference [5].

But the upside with HIIT is that it requires a small time commitment. A study found HIIT to be especially effective for fat loss in overweight or obese people [6].

3 Reasons Why It’s So Effective

A buff person working out in the gym

Here are some of the reasons why HIIT is so effective:

  • It may help increase muscle growth
  • It can reduce blood pressure, heart rate, and blood sugar
  • It’s time-efficient

1. May Help With Muscle Growth

Besides fat loss, HIIT may help you put on more muscle [7].

However, studies have shown that only people who were inactive, to begin with, showed an increase in muscle mass after doing HIIT [8]. This growth mostly happens in the muscles most used in HIIT, the trunk and legs [9].

Weight training still remains the best option for building lean muscle mass everywhere.

2. Reduces Blood Pressure, Heart Rate, and Blood Sugar

HIIT has some important health benefits. Research shows that it can reduce heart rate and high blood pressure in people with obesity, but it doesn't seem to change blood pressure in people within a normal BMI range [10].

HIIT may improve blood sugar in people with type 2 diabetes and improve insulin resistance in healthy people [11] [12].

3. It’s Time-efficient

HIIT cardio workout for fat loss involves long high-intensity intervals followed by short recovery periods. According to various studies, it's one of the most time-efficient ways of working out [13].

Because the average workout takes anywhere from 10 to 30 minutes, people will be more inclined to do it.

Some Safety Tips

A buff person holding a clip board in the gym

HIIT training might be highly effective in burning fat, but you shouldn’t do it very often because of how strenuous it is.

Keeping that in mind, here are some safety tips that will help you reap all the benefits of HIIT.

  • Plan your HIIT workout in advance. Don’t simply do any program. Consult your trainer or physician and follow a routine most conducive to your fitness goals.
  • In my experience, it’s best not to do HIIT more than three times a week. But if you do, ensure there’s at least a 24-hour gap between every HIIT session. Because it’s such an intense exercise routine, your body will need that rest.
  • Make sure you have a nutritious meal and drink plenty of water right after your HIIT workout.

“Everybody is different with unique strengths and weaknesses. Not everyone can push themselves to such an extreme on a daily basis without injury. Meaning for some, doing HIIT three to five times a week feels like a walk in the park while others may need a little less like two to three times a week.”

- Tara A. Nicolas, Nike Trainer & Instructor

FAQs

Which HIIT Is Best for Fat Loss?

Any HIIT exercises that make you expend more calories than you consume are best for fat loss. What exactly that is will look different based on your age, fitness levels, and fitness goals.

Will I Lose Belly Fat By Doing HIIT Regularly?

Yes, you will gain belly fat by doing HIIT. However, since there’s no such thing as spot fat removal, your body will decide when and how much stomach fat to lose.

How Long Till I See Weight Loss Results From HIIT?

You’ll see weight loss results from HIIT anywhere between two to eight weeks. How fast you lose fat depends on your current fitness levels and the amount of work you put in.

Can HIIT Cause Muscle Loss?

No, HIIT in itself can’t cause muscle loss. But if you do HIIT too many times a week without proper rest and nutrition, you may lose muscle mass.

Can HIIT Cause Weight Gain?

No, HIIT in itself cannot cause weight gain. Any weight gain after HIIT may be due to a poor diet and lack of rest.

Are HIIT Workouts Everything You Need to Burn Fat?

If you’re currently doing low-intensity steady-state cardio, incorporating HIIT into your training regimen can help you burn fat more efficiently.

The only downside our clients faced with HIIT is that they were limited to doing it only thrice a week.

So, we usually recommend including some natural fat burners into the mix to help them burn calories on rest days: 

These products that we tested ourselves work well with HIIT to help burn stored fat, reduce appetite, and provide the energy to push through an intense workout.


References:

  1. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0189590
  2. https://www.ncbi.nlm.nih.gov/pubmed/27747847
  3. https://www.ncbi.nlm.nih.gov/pubmed/27368057
  4. https://www.ncbi.nlm.nih.gov/pubmed/26918846
  5. https://www.ncbi.nlm.nih.gov/pubmed/28401638
  6. https://pubmed.ncbi.nlm.nih.gov/26479856/
  7. https://www.ncbi.nlm.nih.gov/pubmed/26479856
  8. https://www.ncbi.nlm.nih.gov/pubmed/25739559
  9. https://www.ncbi.nlm.nih.gov/pubmed/26479856
  10. http://bjsm.bmj.com/content/51/6/494
  11. https://pubmed.ncbi.nlm.nih.gov/29194424/
  12. https://www.ncbi.nlm.nih.gov/pubmed/27346646
  13. https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC6069078/

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