7 secrets Katy Perry has revealed during her Sydney visit.

Image: Katy performing during the Prismatic Tour (Getty)

Unless you’re one of her dedicated Katycats (“fans” to commoners like us), your knowledge of Katy Perry is probably quite limited.

You’re probably aware that she has an affinity for brightly coloured hair and candy-themed outfits, that she used to be married to Russell Brand, and that she may or may not have kissed a girl. You might even know that her real name is Katy Hudson (not to be confused with Kate Hudson) and that her foray into the music world was a Christian rock album.

Until last Friday night (yes, pun intended), The Glow team was largely in the same boat. But when we attended one of the Sydney shows of her Prismatic tour, we learned a whole lot about the 30-year-old’s lifestyle, thanks to her surprisingly open on-stage banter. Here are some of the health and beauty tidbits we picked up:

1. She’s recently discovered she’s gluten intolerant

Poor Katy. Earlier this year, after feeling a bit out of sorts, the singer paid a visit to her doctor and received some sad news. “You get to a certain age, and then one day your doctor of Chinese medicine tells you you’re allergic to gluten,” she lamented during the show, before ‘growing’ a Crust pizza from below the stage (it was a gardening themed segment, if that makes more sense…).

When she gave the pizza away to a young (gluten-tolerant) fan, Katy left the girl with a dire warning - "Your body can change..." - before dedicating her hit The One That Got Away to all the pizzas she'll never get to eat. Clearly she's really bummed about this. But K-Pez, if you're reading this: there are some gluten-free products that don't taste like dust. Consider this post as your guide.

"It’s time to stop pretending you’re gluten intolerant now"

Also, fun fact: Zooey Deschanel, who is regularly confused for Katy (and vice versa) is also gluten intolerant. Coincidence? Or are they really secret twins? We'll never know.

2. You can copy her concert look quite easily

A Katy Perry show is like a sparkly smorgasbord of elaborate costumes, wigs (more on that later), kooky props and colourful makeup. While the rest of us may never be able to get away with wearing a giant, inflatable yin-and-yang dress or a glow-in-the-dark two-piece (well, not in the office, anyway) we can recreate her on-stage makeup quite easily. Even better - you don't need a pop star income to do so.

As a Covergirl ambassador, Katy wears many of the brand's products during her concerts and public appearances. These are the ones her makeup artists use for her performance of Birthday - happily, you can pick most of these up at Priceline:

As for the green wig and printed bodysuit... we can't really help you there.

 3. She grows her own veggies

Like many California natives, Katy is all about healthy living and clean eating - and this is one of the things she loves about Australia. Not content to just buy her veggies from the farmer's market, Miss Perry says she's become a real 'green thumb' at home, growing chives, lettuce, and the ubiquitous kale, which she uses for cooking.

The 5 things nobody ever tells you about kale

"Yes, I grow kale. It's very trendy," she said. She's right, of course - kale has become so popular that we're teetering on the edge of a world shortage of it. Ah well - at least Katy will be well stocked when the inevitable happens.

4. Her fans help her through her darkest moments

Despite her sunny, kooky disposition, Katy has struggled with depression in the past.

In a recent interview with Rove McManus, she revealed she had contemplated suicide following her divorce from comedian Russell Brand. “It was sad and there were thoughts, but there were never actions, thankfully,” Katy said, adding that she wrote her ballad By the Grace of God so anyone feeling the same way would know they weren't alone.

Katy Perry opens up about her mental illness.

During her concert, Katy dedicated the song to her fans, explaining that when she feels sad she reads her Twitter mentions and finds comfort in the messages of love from her supporters.

5. She watches Kath and Kim while exercising

When Katy pulled out the instantly recogniseable, "Look at moy! Look at moy!" during her concert, we realised we had a Kath and Kim fan on our hands. As it turns out, Katy's been watching the quintessentially Aussie show before each of her concerts here.

Katy shared this photo on Instagram, writing: "OZ pre show ritual. 30 mins on the elliptical = 30 minutes of Kath & Kim." As far as rituals go, it's noiiice, it's different, it's unuuusual.

6. She likes to get wiggy with it

One thing that really stood out from Katy's concert was that she rocks a wig like it's nobody's business. I'm not sure her natural hair was on display even once during the two hour spectacular.

Some of her wig-tacular looks included: a Cleopatra bob, bright green 90s buns, an enormous braided switch (clip-in ponytail), a white long bob with rainbow streaks, and cat ears (while performing as her feline alter ego, Kitty Purry). Katy really, really likes cats.

7. She's taller than you'd expect

Emily and I were lucky enough to meet Katy backstage before the show began. We only had a few seconds with her, so while we didn't have enough time to ask her any burning questions, we did get to see what she looks like close up. First of all, yep: her eyes really are as huge as they look.

One thing that surprised us was how tall Katy is. We were expecting her to be Kylie Minogue-petite, because pop stars often are, but she's actually 170 cm. She also looks really fit, which is no wonder - the Prismatic Tour choreography looks bloody gruelling. There are high flying stunts and a whole lot of bouncy dance moves. It's like two hours of straight cardio and she doesn't even seem to break a sweat.

KP, we salute you. And we reckon you deserve a huge gluten-free pizza for pulling that off every single night.

Are you seeing Katy Perry while she's touring in Australia?