Tiffani-Amber Scales Down

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Behind the scenes on a TV set, there are always tons of tasty snacks lying around for the cast and crew. When 19-year-old Tiffani-Amber Thiessen first started playing "Kelly Kapowski" on Saved by the Bell four years ago, she could partake of these tempting treats all she wanted and not add an ounce to her 5'6", 106-pound bod.

But once she hit 17, she noticed a big change.

"Everything just turned around," Tiff tells us. "Hips, thighs...I was like, "Where are these coming from?"

Once, a few days before a beach scene where she had to wear a bathing suit, Tiffani even went on a dangerous crash diet hoping to shed a few pounds.

Unfortunately, when it came time to film a scene, she realized she hadn't lost any weight at all.

"Those types of diets are bad!" she admits now. "I'll never do that again! It was so dumb!"

These days, Tiff keeps her trim body in shape with a nutritionally balanced, low-fat diet — which means no fries or cookies — and a regular exercise program.

I work out," says Tiffani. "I have to."