By SARAH BULL
Ripped: Zac Efron flexes his muscles and delights armies of female fans as he shows off his buff body on the beach on Monday
He had to bulk up to play a marine in his last film The Lucky One.
And it seems Zac Efron has been sticking to the same diet and exercise regime, judging by photographs of the 23-year-old actor on the beach on Monday.
Former High School Musical star Zac showed off his impressively muscular physique as he joined friends at an Independence Day party on the beach in Malibu.
Wearing a pair of low-slung khaki army-print swimming shorts, Zac drew attention to his defined pecs and six-pack stomach as he enjoyed the sunshine over the Fourth of July weekend.
Hanging with friends: Zac celebrated Independence Day with a group of friends
Zac plays Logan Thibault in The Lucky One, which tells the story of a marine who has completed three tours in Iraq before travelling to North Carolina to try and find the woman he believes was his good luck charm during the war.
And while Zac delighted female fans with his shirtless scenes in the High School Musical films, he worked hard to bulk up for his role in The Lucky One - an adaptation of the Nicholas Sparks novel.
Chatting: Zac spent a lot of time talking to a young woman wearing a pretty maxi skirt
Talking about gaining weight and building muscle for the role recently, Zac said: 'It was hard, man. Marines have got this way about them, but they're, like, 50 pounds heavier, so I started training immediately to do the best I could.
'Because it's a kind of sensitive part I care too much about it to let it slide. I really wanted to put in the work.'
Zac was also spotted out shopping yesterday with friends including Rumer Willis in Studio City.
Shopping time: Zac was spotted yesterday out shopping in Studio City with friends including Rumer Willis
Casual style: Zac wore a T-shirt and pair of khaki shorts as he and his friends shopping in stores including Urban Outfitters
Wearing a pair of khaki shorts and printed T-shirt, Zac appeared to be in good spirits as he browsed stores including Urban Outfitters.
Earlier this week, Zac sparked rumours there was something going on with his former High School Musical co-star Ashley Tisdale when he was spotted giving the toned actress a piggy back ride along the beach on her birthday.
However, Ashley was quick to take to Twitter and deny any speculation.
Buff: Zac had to bulk up to play a marine in the upcoming movie The Lucky One
She wrote: 'Don't believe all pictures. People r gonna come up with stuff to say bc it sells!
'I had such a great birthday party with my friends, Family, and BOYFRIEND Scott. I will not let stupid rumors ruin all the fun we had! Xoxo'
Zac and Ashley have remained close friends since they appeared together in the three High School Musical films.