Gorgeous Miriama Smith is usually a shining beacon of good health but right now, the stunning star is on a mission to lose weight, get back into exercise and catch up on some sleep.

It’s usually hard for the energetic actress to stop moving, but a ban on exercise, plus a relaxation of her healthy eating routine and sleep deprivation means the normally svelte 34-year-old has gained 5kg – and some seriously dark circles under her eyes.

While most people would do whatever they could to avoid such a scenario, easygoing Miriama decided to go against her natural instincts to turn herself into a slightly heavier woman who has the effects of stress written all over her face.

It’s a transformation that many would never consider making just for a job, but it’s one Miriama threw herself into head first when working on the TV feature Stolen: The Baby Kahu Story, in which she plays a real-life mother whose baby has been kidnapped.

Miriama’s dazzling smile went on hold for her to get into the mindset of her character Donna Hall, the Kiwi lawyer whose eight-month-old baby, Kahu, was kidnapped at gunpoint in 2002, and who endured nine days of terror as she waitedfor her child’s return.

“I’m normally a happy-go-lucky type of person – I had to do things like not go to the gym so I didn’t have any endorphins,” says the bouncy brunette. “I had a ban on running. My flatmate would say, ‘Okay, no happy-making stuff – just stay inside and be sad!’”

On top of the exercise ban, Miriama put aside her usual healthy eating habits to gain some weight. “I put on about 5kg because Donna is more round in her face. I was eating everything and anything on set – it was great and it didn’t take long!” The physical lengths Miriama went to for the role didn’t stop there. Before she even landed the job, she had decided to pull out all the stops in convincing the casting team she could play Donna.

She explains, “For about three days leading up to the audition I didn’t get much sleep because I was trying to give myself bags under my eyes so I would look like I had lost a child and hadn’t slept for days,” Miriama says.

“I guess I wouldn’t have been top of many people’s minds for this role because I’ve done things like New Zealand’s Got Talent, Dancing with the Stars and Shortland Street – they’re not such gritty roles,” she admits, adding that she is also 10 years younger than Donna was at the time of the kidnapping.

Miriama’s determination paid off when she got the part. But the ordeal didn’t end there – she continued to change herlifestyle and appearance as much as she could. Her hair was cut and dyed black, she stopped plucking her eyebrows and a pair of Donna’s distinctive red glasses were ordered from Paris for her to wear.

However, the most challenging part was still to come. “I have played mothers before, but Donna is the kind of woman you don’t come across often,” says Miriama, who hasn’t met the lawyer but shares a marae in Rotorua with her and spent time talking to people who knew her before filming began.

“I think she can be quite a polarising character,” she says. “She doesn’t suffer fools gladly, she knows what she wants and basically she just moves forward in life – she doesn’t sit there worrying about what people might think.”

Her commitment to playing Donna was so intense, Miriama says getting back to her old self after filming finished was like “an exorcism”.

She laughs, “The first two things I did were wash my hair and pluck my eyebrows. Unfortunately, unlike all those Hollywood stars, I don’t have a million-dollar budget or personal trainers to help me whip off the weight!”

While researching the baby Kahu case, Miriama reflected on the trauma of losing a child in such a way and the difficulty of fronting up to the public gaze. “Donna would’ve had to remove herself so much to speak into a TV camera to talk to this man who had taken her child,” she says. “I’m sure I wouldn’t have been so calm. I don’t think I could even have talked.”

And while Miriama doesn’t have any children of her own, she says she drew on the selflessness and love she sees in her friends who are parents, and imagined how they might react under similar trying circumstances.

“The emotional burden was full-on,” she says. “It’s the toughest role I’ve ever done.”