7 Body Transformations That May Convince You to Try HIIT

Updated: Mar. 18, 2021

Seven women reveal how their body changed when they started high-intensity interval training, better known as HIIT.

HIIT and body transformation

If you want to transform your body with exercise, it’s time to take a HIIT (high-intensity interval training). The workout alternates bouts of intense exercise with less intense “rest” periods to burn fat and calories. “The body will burn calories during the workout, but will also burn fat post-workout due to post-exercise oxygen consumption,” says Cody Patrick, a fitness expert and professional at Sweat440 in Miami Beach.

Unsure whether you should try it?

Here are seven women who tried the HIIT workout method.

Kyra Williams
Courtesy Alexis Picheny/ Kyra Williams

Kyra Williams

“We did group strength training and conditioning circuits that included walking lunges, medicine ball slams, bent-over rows, and a suicide run, all as fast as we could for several rounds. It definitely got my heart rate up,” says Kyra Williams, a personal trainer who first discovered HIIT training through her then-boyfriend. Even for her, she recalls the first workout was challenging.

While Williams was in shape at the time, at 135 pounds and a size six, HIIT training was what finally gave her the super-star strength she craved. She did lose five pounds and one pant size, but it was the muscle definition that was noticeable. For those who want to try their skills in this type of exercise, Williams suggests trial-and-error so you can find a routine that really keeps you engaged. Exercise has many benefits unrelated to weight loss.

Vicki Griffin
Courtesy Vicki Griffin

Vicki Griffin

It was the cardiovascular benefits that piqued Vicki Griffin’s interest in HIIT. After the registered nurse discovered a studio near her that offered classes, she decided it was worth trying it to see if it improved her health and body. More than a year later, she’s still taking five classes a week—and reaping the benefits from her workouts. Not only has she gone from a size 18 to a six and shed 50 pounds, she lost 16 percent of her total body fat.

Griffin’s strength has improved as well—while she couldn’t run a lap, jump up on a six-inch box, do a burpee, or complete more than a few push-ups at the beginning, she’s now able to go above and beyond all of these feats. “I’m always looking for that extra challenge during exercises to get that boost,” she says. The mental perks help motivate her, too: “I noticed the results of the endorphins almost immediately. Even when I’m sore, I always have a positive attitude and a spring in my step. Plus, I sleep like a baby at night.”

For those first starting out, Griffin has a word to the wise: HIIT is hard—but it’s doable, with the right attitude. “You must be motivated and recognize that quitting is not an option. Expect to fail, but then you try and try again until you succeed. Do not give up.” she encourages. Check out all of the ways exercise makes your brain better.

Leigh Ortiz
Courtesy Leigh Ortiz

Leigh Ortiz

Fifteen months after HIIT, Leigh Ortiz is thankful she gave it a chance, since she’s lost 100 pounds and more than 33 percent of her body weight and gone from a size 24 to a size eight. She became motivated after spotting a Facebook ad for Fit Body Boot Camp. “I set small goals throughout my journey to be able to celebrate along the way,” Ortiz says of her success. “My attitude, confidence, and outlook on life all changed for the better because of my HIIT workouts. I am loving the muscle tone that I have; I feel powerful and that I can do any activity instead of sitting on the sidelines. Working out is the highlight of my day and I have to force myself to take rest days now.”

For those who are seeking similar results, she encourages newbies to take the experience at their own pace. “Don’t be embarrassed to ask for a modification—I still do! Go slow and focus on your form. You will be sore, but the crazy thing is that the soreness goes away if you go work out. Keep at it and you will see the results you are looking for,” she says.

Laura Cloonan
Courtesy Laura Cloonan

Laura Cloonan

In 2013, when Laura Cloonan started teaching English at a high school, the job got the best of her. Before then, she had been focused on her health, especially as an athlete, but then she started making food choices she knew weren’t smart in an attempt to deal with the stress of the job. After joining a few gyms where she wandered around aimlessly, she took the advice of a co-worker and gave HIIT a chance. Because the classes were only 30 minutes, she knew she could make the time, and now, she calls it the most effective weight loss program she’s ever tried. She should know, considering she lost 37 pounds in nine months, went from a size 14 to a six, and, best of all, looks forward to working out and teaching—since she’s now a coach, too.

The advice she shares with students—and, of course, reminds herself of too is: Never. Stop. Moving. “It’s okay to move slower, take an extra breath, or grab a drink—but then it’s time to attack the next movement with even more ferocity,” she says.

Amanda Schmidt
Courtesy Amanda Schmidt

Amanda Schmidt

“By incorporating HIIT, I was able to feel and look healthier without investing hours at the gym running on the treadmill for hours. Not to mention research showed that this shorter-duration workout was just as beneficial—if not more—and I was boosting my metabolism, too,” says Amanda Schmidt, assistant general manager of Bulletproof Labs, after recovering from an illness. She began to weave HIIT into her fitness program as a way to build the endurance she had lost.

As a rule, Schmidt judges progress by how she feels and performs rather than how she looks. “I feel energized, youthful, and uplifted. My sleep quality has drastically improved and I fall asleep quickly and easily. I feel like the dense fog that used to cloud my brain has disappeared so that I can now think clearly, focus at work, and stay alert for longer. I’ve also dropped a dress size without losing any weight, which means I’ve exchanged fat for muscle, resulting in fewer inches and a smaller waist,” she explains.

Schmidt says first-time HIITers should aim to train smarter, not harder. “You don’t have to rearrange your entire life or your entire schedule to change your body. You can get better results in less time with this scientifically-backed program,” she says. Learn why HIIT can be an anti-aging workout.

Erika Shannon, Daily Burn Trainer and Movement Coach
Courtesy Erika Shannon

Erika Shannon

In the early 2000s, Tabata training, a particular style of HIIT, was trending. This style includes eight cycles of 20 seconds of super-hard work, followed by ten seconds of rest.  DailyBurn trainer and movement coach Erika Shannon recalls being introduced to this at Equinox in New York City finding it difficult and not loving it. Now, she’s a believer.

Most dramatically, HIIT has changed how she feels about her body, especially improving her sense of confidence and strength. “HIIT training within my workout regimen keeps me in excellent cardiovascular shape. These type of workouts have also changed my life as a busy working mom because they are so quick; I feel like I get a good sweat in and I can easily fit it into my schedule,” she says.

Her best advice for novices is to make sure you’re challenging your heart rate, since hey, that’s the goal. You also don’t want to push so hard that you have to take a long rest, since you’ll lose the benefits. “If the move is too advanced for you, you can still do something else with full exertion for that period of time, or modify the exercise so it suits you,” she recommends.

Allie Schweitzer
Courtesy Allie Schweitzer

Allie Schweitzer

“I’ve seen other women with defined muscles, but never thought that would, or could, be me. I still have a long way to go, but I am as excited as ever to see what I can accomplish,” says Allie Schweitzer about doing her HIIT class Shred415. Her co-worker had to drag her to her first class, but Schweitzer is now so grateful for the extra push. It was love at first sweat. In her first six months, she’s dropped weight and inches in her stomach, arms, and legs; her clothes fit better; and her muscle definition is more apparent. It’s been a transformation that’s both built up her self-esteem and surprised her.

For Schweitzer, the greatest hurdle was simply getting started. That’s why she encourages everyone—and anyone—to, well, go. “The first class is daunting, but everyone starts somewhere,” she says. Trouble staying motivated? “A workout that changes moves constantly will help you stay focused while engaging muscles you didn’t even know you had.” Next, check out some more of the most motivational before-and-after photos.