Leasha West's body has been through the wringer.

As a U.S. Marine Corps veteran and former combat instructor, she hiked 15-plus miles several times a week with a 150-pound pack on her back. The bottoms of her feet turned raw and blistered, her toenails fell off, her legs went numb. "It's not uncommon to have blood in your stool" from the training regimen, says West, who served from 1998 to 2002. "My body took a serious beating."

But the 45-year-old – who lives in Kalamazoo, Michigan – hasn't stopped. In addition to working toward her MBA while running her own financial services and insurance agency, she regularly lifts weights and swims.

And, for a few minutes almost every morning for the past three years, she's stepped, nearly naked, into a negative 250 degree F (or colder) chamber. That's more than twice as cold as dry ice.

"It's the best way to start (the day)," says West, who pays $169 a month for unlimited treatments – called whole body cryotherapy – although single sessions can run up to $100 in some areas of the country. What for? Initially, to ease her back pain and muscle stiffness after hearing rave reviews from her professional athlete clients. But West has continued the treatments because she finds they lead to benefits including more energy and focus, a boosted metabolism, improved tolerance to cold and pain, faster-growing hair and nails, younger-looking skin and sounder sleep."I can really tell the difference ... when I skip a few days," she says.

What Is Cryotherapy?

Whole body cryotherapy, which essentially means "cold treatment," is a procedure that exposes the body to temperatures colder than negative 200 degrees F for two to four minutes. While it's been used to treat conditions such as multiple sclerosis and rheumatoid arthritis in Japan since the late 1970s, it's only been used in Western countries for the past few decades, primarily to alleviate muscle soreness for elite athletes, according to a 2015 Cochrane review of four studies.

But now, spas, gyms and cryotherapy facilities are advertising benefits including weight loss, younger-looking skin, better mood, more energy and more – despite the fact that it's not regulated by the U.S. Food and Drug Administration. Even Cryohealthcare, a company that makes cryotherapy equipment, notes that the therapy"is designed to supplement health and wellness programs, without treating any medical diseases, disorders or illness."

"While it seems like there could be some beneficial outcomes from it, this doesn't seem to be a breakthrough technology innovation that's going to change medicine," says Dr. Hallie Zwibel, director of sports medicine at New York Institute of Technology College of Osteopathic Medicine on Long Island. "At this point, it seems to be an adjunctive type of treatment."

What Can You Expect From a Cryotherapy Session?

Depending on the facility, you may be given gloves, socks, slippers, a face mask, ear muffs, underwear or all of the above to protect sensitive skin before stepping into a cryotherapy chamber. While it feels cold right away, the time passes quickly, West says. "You're going to get the shivers; you're not going to feel like you're frozen," she says, noting that the treatment just penetrates the skin, so the organs stay safe. Plus, she adds, "you can open the door at any moment to get out."

Potential Cryotherapy Benefits

Purported cryotherapy benefits include:

Muscle and joint pain relief

Weight loss

Younger-looking skin

Better mood and energy

Muscle and Joint Pain Relief

If you've ever iced a twisted ankle or sore shoulders, you've treated yourself to a form of cryotherapy that works. Applying cold to an injury for 15 minutes at a time, three to four times a day is "highly effective," says Jon Schriner, a fellow of the American College of Sports Medicine who's based in Michigan. But the benefits of doing that to your whole body are less established.

One 2017 review of studies on athletes in the International Journal of Sports Medicine, for instance, suggests that cryotherapy can be effective in reducing muscle pain, inflammation and cell damage. Research has also shown that athletes may feel like they recover more quickly when they use cryotherapy, "which is important," Zwibel says. Still, the research isn't robust enough to dictate how long, how often and at what temperatures cryotherapy may work best, if at all.

Weight Loss

The theory behind cryotherapy for weight loss is that cold temperatures force your body to work hard – aka burn calories – to stay warm. Cryotherapy spas claim a single session burns hundreds of calories and that repeated use can boost your metabolism, helping you burn more calories all day.

West, for one, notices the difference in her tolerance of Michigan weather. "My metabolic rate has increased, so I don't get cold," she says.

In reality, though, there are better ways to lose weight. "Being cold does boost metabolism by trying to warm the body," but it's a stretch to sell it as a weight-loss therapy, Schriner says. For a better shot at weight loss, you'll probably have to change your eating habits, says Susan Albers, a psychologist at the Cleveland Clinic who specializes in eating issues and weight loss. "(Whole body cryotherapy) is a three-minute treatment, and we're always looking for that thing to solve our issues an easy way," she says. "It doesn't work that way."

Anti-Aging

Since beginning regular whole body cryotherapy treatments, West says her skin looks better than it has in a long time. "This is taking a lot of years off," she says.

But Dr. Marie Jhin, a dermatologist in San Francisco, doesn't suggest people seeking the fountain of youth put their money on it. "With the decrease of temperature, it helps decrease inflammation, so a lot of times, people believe that decrease in inflammation can help with a lot of … inflammatory problems or skin issues," she says. "But it's not long term."

It's better to do what's known to work: Protect your skin from the sun, don't smoke and consult with a dermatologist about FDA-approved treatments such as prescription topicals or dermal fillers. "There's not one thing that helps with anti-aging," Jhin says, noting it depends on your skin condition and how much you want to spend. "It's about being healthy and avoiding things that aren't healthy and doing treatments that are good for your skin."

Anxiety and Depression

For West, stepping out of the cryotherapy chamber elicits "a very euphoric feeling," she says. After all, she survived! But while the procedure might temporarily boost your mood and energy levels, most studies looking at whether it can help treat mental illness aren't strong or large enough to draw conclusions, Albers says.

"The theory behind it is that it releases endorphins and your natural adrenaline, and it gets your blood flowing throughout your body, which is something that can be helpful for people who are experiencing anxiety and depression," she says. "But I'm not sure how long term [it works]."

Plus, anxiety and depression are complex conditions best treated by a mental health professional, Albers says. Of course, no one's stopping you from doing both. "With any kind of [alternative] therapy like this … it's often a nice adjunct to some of the traditional things that you do," she says. "That could be another way of looking at it – combining it with other treatments."

Is Whole Body Cryotherapy Safe?

Cryotherapy isn't safe for everyone. The treatment shouldn't be used by pregnant women or people with various health conditions, including severe hypertension and various heart problems, warns Cryohealthcare. Children under 18 need parental consent.

Zwibel notes that folks with an allergy to cold or a nerve problem like neuropathy could worsen their conditions if they try cryotherapy. And, while the treatment seems to be safe when used correctly (for instance, in short spurts, under supervision and without wet clothing that can freeze and cause frostbite), it can cause skin irritations similar to a windburn or, in rare cases, even be fatal: The treatment caught the public's attention in 2015, when a cryotherapy spa employee died after stepping into the chamber unsupervised, and never stepped out. More recently, a New York woman reportedly filed a lawsuit against her gym and a cryotherapy company after the procedure left her with what she said was permanent scarring. Because the procedure is not FDA-regulated, you'll have to do your own due diligence to find a facility, if any, you trust.