It requires a lot of discipline to look as good as Molly Sims.

The 38-year-old model-turned-actress covers the January issue of Shape, where she admits her incredible physique "does not come naturally. I wasn't born with this body."

"I have to work out 60 to 90 minutes at least five days a week and stick to a high-fiber, low-calorie eating plan," Sims explains.

The Project Accessory host wasn't always so dedicated to her health. After a string of fad diets and erratic workout routines, Sims was determined to find something that would stick.

"I wanted to be consistent with my exercise, so I committed to working out for 30 days in a row, no matter what," she tells Shape. "For an hour every day, I did something. I was on the elliptical or the treadmill, and if someone asked me to go to a class -- whether it was spinning, boxing, yoga, you name it -- I went."

Sims, who recently wed movie producer Scott Stuber, 42, eventually fell in love with the gym.

"By the end of the month, I felt so good, I just kept going," she recalls. "I didn't want to lose my momentum."