If you’ve been hearing a lot about HIIT, or high intensity interval training, lately, you’re definitely not alone. HIIT has taken the fitness world by storm over the past decade or so, with more people discovering it as an efficient means of getting an intense workout.
But what exactly is it, and is it better than old-school cardio exercise, or cardiovascular training, for weight loss?
What Is High Intensity Interval Training, or HIIT?
Jessica Mazzucco, a New York City-area certified fitness trainer and founder of the Glute Recruit, says that HIIT is “an extreme type of workout program that builds endurance, strength and helps shed weight more quickly than low intensity cardio.”
In fact, HIIT is a type of cardiovascular exercise, but it’s done at very high intensity levels that are interspersed with rest periods, or intervals, that allow the body to achieve a higher heart rate for short periods of time. To access that high intensity threshold, you “should be nearly out of breath or unable to hold a conversation,” Mazzucco says, which usually occurs when you reach 80% of maximum heart rate.
Some super-high intensity HIIT workouts will take you right up to 90% or 100% of your max heart rate for a short time to really crank up the heat. To calculate your max heart rate, subtract your age from 220.
Many people really enjoy this super effort, says Joel Freeman, a Beachbody Super Trainer and creator of LIIFT4 based in Los Angeles. “People love that overall feeling of going to 90% to 100% of your max heart rate. You feel like you’re getting more of a workout because you’re breathing heavier and your muscles are burning.”
Often, rest periods in HIIT workouts incorporate active rest, a type of light activity like walking or jogging, that lasts longer than the amount of time you’ve spent on the strenuous exercise element.
Most HIIT workouts are completed in 10 to 30 minutes, which is often less time than you need for a full cardio conditioning or strength training session. A HIIT workout “consists of intervals of intense bursts of energy followed by little to no rest,” Mazzucco adds.
This is a big part of the appeal and why it’s become so popular in recent years, Freeman says. “People are always looking for the biggest bang for their buck in the shortest amount of time,” and HIIT fits that description when compared with “traditional cardio which tends to take longer.”
Benefits of HIIT
And there are real benefits to the HIIT approach to fitness, Mazzucco says. “HIIT is a great way to lose weight in less time. Most people can burn the same number of calories in a 20-minute HIIT workout than they can in performing constant cardio or strength training for 45 minutes. HIIT also increases lung capacity and blood flow within the body.”
Freeman adds that “spiking your heart rate” offers “a lot of aerobic benefits and you’re using more muscles. So, you get a higher metabolic burn in a shorter amount of time.”
HIIT can also increase your resting metabolic rate, and you’ll “continue to burn calories for up to 24 hours post-exercise,” Mazzucco says. It can help burn more fat rather than muscle, which can occur with steady-state cardio.
Plus, it can help you trim your waist. “People can continue to grow their muscle mass while shedding extra fat in hard to reach places like the lower abdomen and thighs,” Mazzucco says.
Limitations of HIIT
But there’s a limit to what HIIT can do, says Thomas Roe, a fitness trainer and endurance athlete based in San Antonio, Texas. “High intensity interval training — think group or circuit training and moving from station to station with little to no down time — can assist you in dropping the weight, as long as it’s combined with a low-calorie diet or nutrition plan.”
What you do in the gym has to balance with what you do in the kitchen, he explains. “You can’t out-train a bad diet. If you’re burning 2,500 calories a day but consuming 3000+ calories, you’re putting on weight.”
What Is Cardio Training?
On the other hand, what’s thought of as traditional cardiovascular exercise has long been a go-to activity for people trying to lose weight. Cardio exercises include “any form of exercise that elevates your heart rate and oxygen and blood flow throughout the body while using large muscle groups,” Roe explains. Common examples include:
— Running or jogging,
— Long distance swimming.
— Treadmill or elliptical machine work.
Cardio can “help you lose weight provided you continually operate at a caloric deficit,” Roe says.
A cardio workout typically lasts “a minimum of 20 to 30 minutes at 60% to 70% of your maximum heart rate,” Freeman explains. However, “that can be boring for a lot of people, like myself. I don’t have any interest in doing that,” he says. Traditional cardio training tends to take longer and doesn’t have as many super intense spikes of activity during that period as HIIT workouts do.
But it’s good for building endurance and stamina and can be an important component of using exercise to support weight loss efforts, as it can help you burn calories and fat. Cardio “helps the body burn enough calories to reach what’s called a calorie deficit,” Mazzucco says.
Janet Lee, a doctor of Chinese medicine, yoga instructor and health journalist based in Kansas City, Missouri, says that calorie deficits are important for losing weight, and while you can achieve some of this with exercise, “you really have to dial in your diet. There’s really no getting around it,” she says. “Try to limit your portions and limit your calories. It’s calories in, calories out, for the most part.”
In addition to helping support weight loss, cardio, as the name implies, is also really good for your cardiovascular system, or your heart and lungs. It helps strengthen the heart and improve endurance, which are key components of overall health, wellness and longevity.
“Cardio is great for the cardiovascular system and overall fat burning,” Freeman says. “Plus, it releases endorphins,” the brain chemicals responsible for creating the sensation of a runner’s high. “That sense of accomplishment comes with cardio,” he says.
Which Is Better for Weight Loss?
For busy folks who are trying to find time to fit in exercise, there’s certainly an efficiency appeal to HIIT workouts. And if you’re trying to lose weight, it can help. But, Freeman says, “I always hesitate to say one is better than the other because there’s details that go into the question. When I’m working with clients and writing my programs for Beachbody, I ask, ‘How much time do you have? What are your physical limitations?’ And it depends on the person and the circumstances.”
Roe agrees that both cardio and HIIT are good choices for controlling weight, provided they’re “paired with a proper nutrition plan.” In fact, he says it’s a good idea to “incorporate both to break up your routine and shock and shape the body.”
If you’re very overweight or trying to start from scratch in getting into shape, Freeman recommends starting with lower intensity workouts and modifying them for what you’re able to do, rather than trying to jump right into HIIT workouts. You’re less likely to get injured if you ramp up slowly.
Mazzucco agrees that while HIIT might be more efficient, “it shouldn’t be performed every day. HIIT workouts are hard on the body and should be alternated between less intense workouts like walking or yoga to avoid injury.”
In short, your body needs time to recover in between workouts. “If you’re feeling fatigued with heavy legs or difficulty performing your daily routine, it might be a sign that you’re overdoing it with HIIT exercise,” Mazzucco says.
Indeed, Lee says that overtraining can happen fairly quickly if you undertake too many HIIT workouts in a week. “You don’t want to be doing HIIT every day, as you’ll be overtraining and you’ll be exhausted and won’t be getting all the results out of your workout. So, I think it’s great to aim for two to three high intensity workouts a week,” and then mix in strength training and cardio on the other days.
Making Exercise a Daily Habit
When it comes to choosing the best exercise to support weight loss efforts, Mazzucco says “the key to approaching working out for weight loss is to find a type of exercise that you enjoy. Exercise should be a time of day that you look forward to and not dread.”
If you hate working out, you’re probably engaging in the wrong type of exercise. If you’re struggling to find the right protocol for you, consider working with a trainer, as they may be able to introduce you to new options that you haven’t thought of yet.
In her book “20 Minutes, 4 Weeks, 1 Dynamite Body!: Tone & Trim in No Time” Lee offers a variety of quick workouts that include a mix of strength, HIIT and cardio work that can be completed in a short time each day and with minimal equipment. “You don’t need a ton of gear. You can do a lot with just your body weight,” so that removes another potential excuse, she says.
“A lot of people don’t have time to get to the gym, and the idea of doing an hour is just off-putting,” she says. But her approach features full workouts that include a warm up, workout and cool down.
If doing just 20 minutes makes exercise more approachable, then start there, Lee says. “I think any health expert or epidemiologist will tell you that anything is better than nothing. So, if you can go out for a five-minute walk or a 10-minute walk, that’s great.”
And when you’re working out, even if it’s just 20 minutes, “try to make the most of it. If you’re just going to walk on the treadmill for 20 minutes, that’s better than sitting on your couch. But if you’re going to do 20 minutes, try to get your heart rate up, get the intensity up,” which you can do by increasing speed, incline or both to make a more challenging workout. Use that 20 minutes to work hard, and you may be able to burn as many calories as you would in 30 or even 45 minutes, she says.
Roe recommends enlisting the help of a “fitness trainer who has experience with weight loss.” And he says it’s a good idea to “enquire about their own personal journey or struggles with weight.” Trainers who have successfully managed their own weight are “generally the best because they can relate to your journey and help devise a plan and schedule to reach your goals,” he adds.
Building Muscle Helps With Weight Loss
And don’t forget to include some strength training workouts too, Freeman says. His LIIFT4 program is structured around four days a week that combining lifting with HIIT, to provide the benefits of HIIT with strength building.
As you build more strength and muscle, you’ll end up burning more calories 24/7, as muscle burns more calories than fat. Mixing up workouts and engaging in a variety of workout types helps prevent burnout and can help you avoid injury.
If you’re using a wearable fitness device that tracks calories burned, Freeman says it’s best not to get too hung up on the calories burned just within the workout, but to look at the bigger picture of the calories burned throughout your whole day. “Turn your body into a calorie-burning machine not just for the workout, but throughout the rest of the day. Sustained weight loss is more attainable by increasing muscle mass,” which can boost your metabolism.
Roe also recommends setting realistic goals and understanding that “exercise and weight loss don’t always go together hand in hand.” Finding someone who can keep you accountable, such as a trainer, support group or team, can help you stay the course.
Lastly, Mazzucco adds that “weight loss is a journey and doesn’t happen overnight. It’s important to be patient when losing weight and not become discouraged.” And consistency is key — factor in time to work out each day, just like you do for meal planning. “Essentially, make it a non-negotiable part of your life.”
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Update 01/11/22: This story was previously published at an earlier date and has been updated with new information.