50 Cent has revealed plans to back a campaign that aims to wean children off chips, burgers and other junk food.

The G-Unit rapper, famous for his washboard stomach, is to be the judge and spokesman for a high school cookery competition in the US that aims to prevent obesity.

The singer, despite his muscular frame, says he was not always in shape. "I had all the unhealthy habits, soda, a lot of fast food, all those things."

Whichever contestant makes the most nutritious meal will win a $100 000 scholarship to a US university.