Olivia Munn believes the secret to her weight loss is chomping on beef jerky.

The 36-year-old actress has claimed her weight kept fluctuating when she was shooting 'X-Men: Apocalypse', which saw her lose a ''bunch of weight'' as she worked out, but re-gain the pounds because she used to snack on protein bars.

However, the brunette beauty decided to swap her sugar-filled snacks and Greek yoghurt for the meat feast.

Speaking to E! News about her healthy eating regime, Olivia - who portrays Psylocke in the fantasy film franchise - said: ''Two years when I was shooting 'X-Men' I lost a bunch of weight working out and doing martial arts and didn't even realize it.

''[I started] reaching for protein bars a lot because I thought that was being healthy.

''I love jerky first of all, but then I looked and it was a lot less sugar and carbs and it was super high in protein. It was a lot easier than carting around a Greek yogurt because that's what I was doing at the time.

''That's when I started levelling off my weight.''

And the star believes the lean slithers of protein, which she has likened to ''steak in a bag'' helped her to cut the weight.

She added: ''I was able to maintain it because it's so delicious. It's like steak in a bag.''

Olivia has revealed as well as eating lean meats, she also practices Tae Kwon Do' to stay in shape, which is a sport she practiced during her younger days.

She said: ''I did Tae Kwon Do growing up and started again for 'X-Men'. That's the one thing I've been doing.''

However, the model doesn't enjoy spin classes, and prefers to do ''a million squats'' if there is a goal at the end to achieve.

She said: ''People go crazy for it [SoulCycle] and I just can't do it. I have to do something where there's a goal. I'll do a million squats if it means I can learn to do this 360-degree kick.''