Showing their support! Reese Witherspoon and Renee Zellweger keep it simple as they dress down for ALS walk

They are Hollywood royalty, but Reese Witherspoon and Renee Zellweger didn't need a red carpet to entice them out on Sunday.

Instead the actresses pulled on their Team Nanci T-shirts and set off on a 1.6 mile sponsored walk in Exposition Park in Los Angeles to raise funds for research into ALS on Sunday.

Their longtime personal publicist, Hollywood powerhouse Nanci Ryder, has been fighting the horrific disease since last summer.

ALS, or amyotrophic lateral sclerosis, is a fatal progressive neurodegenerative disease that affects nerve cells in the brain and the spinal cord.

Average life expectancy of a person with ALS is two to five years from diagnosis.

Nanci was fit enough to be at the event, although she can no longer speak.

They were joined by Courteney Cox, 51, who also wore a black Team Nanci T-shirt.

Last year, after learning of Nanci's diagnosis, Reese, 39, said: 'It was devastating. We just cried and cried and then said, "What are we going to do to get busy to change things?" '

Other celebrities at this year's 13th Annual LA County Walk To Defeat ALS included superstar Miley Cyrus, 22, and Pilates expert Mari Wilson, who both took to the stage to lead a class.