Natasha Bedingfield is a cute and successful British pop singer - you may have heard her moving song "Unwritten," a.k.a. the theme from The Hills, a couple of million times, as well as some of her other hit singles.

But this songstress also loves to work out!

The 5-foot-6 performer recently lost 15 pounds in four months - and her secret is (you guessed it) cardio and moderate dieting!

Now 15 pounds lighter, Natasha Bedingfield sticks primarily to lean protein and veggies when it comes to her diet, and works out a lot.

When she's not in the gym with her personal trainer, she's enjoying the outdoors with her L.A. businessman beau of two years, Matt Robinson.

"We run and go hiking," Natasha says of her simple, but effective celebrity weight loss regimen. "He's very built. Everyone thinks he's my bodyguard!"