Williams driver Nico Rosberg has been busy losing weight in a bid to increase his chances of F1 success in 2009.

The 23-year-old finished 13th last season but longs to challenge Lewis Hamilton for the title. And with Formula One cars having undergone a major design overhaul because of sweeping rule changes, Rosberg is making sure he gives himself every chance.

He said: "I'm really determined to get the best out of myself. I'm always improving my training and everything else that makes me become the best possible racing driver."

One of the most significant changes made this year is the introduction of Kinetic Energy Recovery Systems (KERS).

KERS stores energy from braking and allows the driver to re-use it for a short burst at the press of a button and the cars have also been redesigned at the front and the back with a view to increasing overtaking.

Rosberg added: "This winter has also required me watching my weight. It has always been an issue in F1 but now more so than ever because of KERS, which is in the back. With this year's rules it is beneficial to be a bit further forward so the weight has become more important than ever.

"I don't want to put a number on it but it is a whole new area. You have to put effort in food-wise and also muscle training to make sure you don't bulk up. There is a whole science behind it."