Making time to go to the gym, however, just "felt like torture," the actress, 23, tells Shape magazine in its January issue
But after suffering a back injury on the set of The Suite Life of Zack & Cody and discovering her family's history of diabetes, Tisdale realized it was time to make a few changes in her life – starting with her attitude.
"Now before I work out," she says, "I think, 'I love exercise' – and it works."
Getting FitTo kick things off, Ashley started working with LA-based trainer Christopher Hebert eight months ago. She does an hour-long workout three or four days each week consisting of 30 minutes on the elliptical and 30 minutes of weight training and core exercises to keep her back strong.
One exercise has Tisdale running up and down a set of stairs with a weighted medicine ball held overhead. Her workout routine can be tough, but Tisdale says her trainer is her secret weapon.
"He's cute, which makes it fun," she says. "And he never lets our exercise sessions get boring."
Now that Tisdale is finally having fun in the gym, she has also started to feel some of the positive side effects.
Before exercising, "I was always super-thin – too skinny, actually," she says. "I felt like someone could break me in half. I realize now that being a bit more curvy and toned is so much more beautiful."
In the Public EyeTisdale also credits her mother, Lisa, with helping her avoid the pitfalls of Hollywood stardom at such a young age.
"My mom never drank or smoked," she says. "I learned from her to embrace being different rather than be intimidated by it."
Tisdale put her mother's advice to the test last year after undergoing surgery for a deviated septum that was affecting her voice, something she had struggled with since she was 14 years old.
"I had to recover from the operation in front of the whole world, and a lot of photos were taken of me while my nose was still swollen," Tisdale says. But "some people made a big deal out of it, saying I had plastic surgery to change the way I look."