Just like that, it's February. 

One exercise-tracking service estimates most people who commit to a New Year's resolution give up before their first month's gym membership expires. Quitting day, it calculated, was Jan. 19. 

But instead of starting resolutions to exercise more, eat healthier or drink less alcohol, many people have opted to attempt lifestyle overhauls by trying wellness-related social media challenges. One of them, 75 Hard, has been popular for years, particularly on TikTok, where its related hashtags have been used more than 2 billion times.  Many who've completed the challenge profess it as life-changing, having led them to significant weight loss and newfound control of their eating habits. The results are out there in the form of thousands of before-and-after posts. 

Yet, many others, including fitness experts and some who've attempted the challenge, wouldn't recommend it. They point to its extreme nature, vague guidelines and the likelihood that when the grueling test is over, people will just revert to their old ways. 

Boyd Crockett, of Calgary, completed 75 Hard late last year. 

The 46-year-old home inspector lost about 20 pounds, which he credits to the program forcing him to cut out his junk food snacking habit. 

Created by Andy Frisella, the host of the Real AF podcast, 75 Hard is dubbed a "mental toughness program." 

Frisella clearly states it's not a fitness program, and he advises people to check with their doctor before starting. 

The program lasts 75 days, hence the name. The rules are simple. 

For Crockett, the program provided structure, a goal and a challenge he thought he could handle. 

"I don't believe in New Year's resolutions. I never have," he said. "With this program, I knew what I had to do every day. And if I didn't do one of those things, I failed and had to restart." 

Roman Thauern, a Calgary-based sports scientist, took one look at 75 Hard's rules and almost immediately said he wouldn't advise it to anyone.

"To summarize it, way too general, in my opinion, for the public — and I think it's also too aggressive for 75 days straight," he said. 

He found the workout regiment, with no rest days, potentially harmful. 

As for the daily progress photo, Thauern said that some people could develop unhealthy body perception issues. He also questioned the point, as day-to-day changes would be imperceptible. 

Yet, he wasn't surprised to learn 75 Hard had gone viral. 

Crockett learned about 75 Hard through social media, where testimonials abound, complete with before-and-after photos. 

He started 75 Hard in late September. Five days in, he failed. He ate a "cheat meal" to get his blood sugar up after a workout. 

"I just started the next day, and went 75 whole days," he said. 

For his workouts, he kept them varied. One day he'd lift weights in the basement, the next day he'd do a core-based yoga session. 

As the days went by, Crockett began to feel lighter. With his slimmer build, tying his skates before a hockey game was no longer a struggle. 

"I could hardly breathe before because I had this big stomach," he said. 

After completing the challenge, Crockett was proud of himself. Like quitting alcohol years before, he had accomplished another hard task. 

While he did return to snacking over the holidays, it was at a lesser degree than before. He also said that he continues to workout consistently, although not every day, and still reads every morning. 

"I'd say for anyone to do [75 Hard], it'll change their life." 

The rigidity and intensity of 75 Hard has led some to create a toned-down version of the challenge, sometimes called "75 Soft."

This altered version strays away from the strictness of the original, and cuts out the punitive first rule. In other words, skip days are allowed. 

Yet the goal remains to eat healthier, workout almost daily, drink lots of water and read 10 pages a day — for 75 days. 

Stephanie Borgland, a professor at the University of Calgary who studies behaviour, said that whether or not someone completes the hard or soft challenge, doing something consistently for over several weeks will help build a habit. 

However, that doesn't mean that at the end of 75 days, people will have manifested a lifestyle change, even if they do lose weight or get a grip on their eating habits. 

Borgland noted that in the reality TV show The Biggest Loser, contestants would quickly lose huge amounts of weight. Yet, after the show, researchers found that almost every contestant gained the weight back. 

Thauern, the sports scientist, says the 75 Soft challenge appears to be a more workable path for people trying to adopt a healthier lifestyle. In particular, he liked that people could take rest days without having to start over.

"People are way more motivated long term by reward, not by punishment," he said. 

"Overall, it should be a lifestyle, not something you do for a while.… You have to ask yourself, 'Can I do that for the rest of my life? Or at least for a really, really long time?' If the answer is no, you probably shouldn't commit to that."