Most women diet to look good in a bikini.

But Alexandra Daddario did the opposite; she started eating more so she could build muscle mass, the beauty told the June issue of Women’s Health.

‘It was kind of amazing, the transformation I went through,’ the 31-year-old brunette looker, who has been romantically linked to her Baywatch co-star Zac Efron, said.

Flawless: Alexandra Daddario started eating more so she could build muscle mass to look good for Baywatch, the beauty told the June issue of Women’s Health

Toned: ‘It was kind of amazing, the transformation I went through,’ the 31-year-old brunette looker, who has been romantically linked to Zac Efron, said

‘For Baywatch, I started doing weight training, which I had never done before, and I saw a huge difference,’ explained the San Andreas star.

Daddario worked with Efron’s personal trainer Patrick Murphy because she figured: ‘Patrick trains Zac; Zac’s body is insane.’

They went at it up to five-day-a-week with very intense sessions that lasted an hour.

With her Rock: ‘For Baywatch, I started doing weight training, which I had never done before, and I saw a huge difference,’ said the San Andreas star

Lovely trio: Alexandra with Kelly Rohrbach and Ilfenesh Hadera on the set of Baywatch

Murphy had her use free weights, sliders, TRX straps, resistant bands and BOSU balls, she told Women’s Health.

And she admitted that sometimes she worked so hard she was ‘overwhelmed’ and felt ‘nauseous.’

‘Really, I’ve never done anything where I’ve thought about my body as much,’ the former model said.

‘You are literally in a bikini the entire day. I even wore a swimsuit when I auditioned with Zac.’

She used to OM more: ‘My normal workout routine, pre-Baywatch, was a lot of hot yoga,’ she told the magazine

Another look at the three amigos: The ladies on a boat as they bob in the water

She said she still workout out with Murphy, but instead of five times a week, they meet only twice a week.

This is a big change from her routine before Baywatch – which also stars The Rock and Priyanka Chopra.

‘My normal workout routine, pre-Baywatch, was a lot of hot yoga,’ she told the magazine.

Two cute: With her co-star Efron in Australia earlier this week

‘I feel like it helps with anxiety, it helps with sleep, it was sort of more of a mental thing.’

But the star says she has for years followed a very healthy diet.

‘As I’ve gotten older, something that made a huge difference for me was being healthy,’ said the True Detective actress.

‘It’s not about how much you eat…it’s eating healthy food and eating when you’re hungry, and not thinking about it so much.’

Baywatch opens May 25 in the US.

She can’t keep her clothes on! The stunner in a bikini for GQ Mexico