R&B star Ashanti jumped at the chance to be a part of U.S. First Lady Michelle Obama's new hip hop health initiative because she knows just how it feels to constantly be worried about her shape.

The singer has joined a group of artists who are making up Obama's Hip Hop Public Health Foundation, and together they're releasing an album of uplifting music for teens in October (13).

Ashanti admits that although she has never had to worry too much about her health and fitness, she has always been careful about what she eats.

She explains, "As a public figure, you always have to worry about, 'Do I look Ok? Are my arms too big? Are my legs big...?'

"And you have to constantly try to be in shape, so you don't give people too much to talk about."

Ashanti hopes the Hip Hop Public Health Foundation gives youngsters the encouragement they need to get healthy and stay fit, adding, "The message is believe in yourself, believe you can do big things and dream big... Be fit and be healthy."