Sister Act star Kathy Najimy shed a staggering 50 pounds after realising she was too out of shape for a TV movie role she had been offered.

The actress admits scenes that called for her energetic character to run, squat and jump left her out of breath and she decided it was time to watch her weight.

Najimy tells Access Hollywood Live, "I had some joint problems and so I thought, 'I should get healthy,' so I did a lot of exercise... and (ate) low-fat food."

And the star admits a zumba dance class really helped: "Zumba I really like a lot... (It works) if you have a hot teacher like I do... I get there at 11 o'clock with lip-gloss."