"Having to exercise twice a day and be strict on my diet were really uncomfortable and new areas for me to tackle, because I hadn't had that conversation before," she says.

But since completing the challenge, she's noticing the lasting impacts so far.

"I exercise a lot more regularly, my reading habits and my relationship with food have transformed," she says.

While 75 Hard has turned into a viral craze over the last few weeks, it was actually invented back in 2019 by author and podcaster Andy Frisella.

He said on his podcast that he's spent "20 years figuring out how to master mental toughness" and has used this knowledge to create the plan.

He is not a qualified personal trainer or doctor and does not give guidance over what classifies as a healthy diet in the plan, but it's understood to mean balanced and nutrient-rich.

More relaxed variations of the challenge have been popping up on social media recently, called 75 Soft and 75 Medium, in which participants can have the odd alcoholic drink and unhealthy meal while still doing exercise and reading.

"I definitely think there are elements people can implement, committing to 45 minutes of daily movement, being conscious of drinking more water and reducing screen time, but you need to be aware of what's involved," Tana adds.

Another aspect is motivation. "There is so much pressure for people to transform their lives at this time of year," she says.

She suggests finding a way to "challenge yourself while also being kind", so that you add fun and value to every day, without exercise and food feeling like a punishment.

From a medical perspective, it is difficult to determine whether 75 Hard is beneficial.

NHS GP Sam Whiteman points out that, because "it has not been studied" in a clinical setting, it cannot claim to change your life in any way.

He also says that it would need to be compared to a more basic regime, to see if that could achieve the same results.

"If it's a way for people to get out and be active then I am all for it, but if it's a question of whether this is better than going to the gym three times a week or going for a run once a week and eating healthily, then I am not sure," he adds.

Hitting certain criteria isn't the intention of 75 Hard's founder, Mr Frisella. He doesn't set any rules that involve losing a certain amount of weight, for example.

While the challenge encourages people to take progress pictures each day, much of the TikTok content around it focuses on how the person feels at the end rather than how they look, helping to avoid unhealthy fixations with appearance.

Dr Whiteman recommends visiting the NHS Live Well website, external, which has tips on what constitutes a healthy weight, diet and exercise regime, along with mental health and sleep advice.