Jessica Biel, Scarlett Johansson and Jessica Alba pile on pounds for hilarious TV spoof

Actresses Jessica Biel, Scarlett Johansson and Jessica Alba appeared in a hilarious TV spoof to poke fun at extreme weight loss 'infomercials'.

Biel, 29, Johansson, 26, Alba, 29, and other stars took part in the new parody skit on American late night chat show Jimmy Kimmel Live.

The three, who lead the group of stars, claimed to have been converted to the 'Jimmy K' diet plan, and their faces were superimposed on to pictures of decidedly portly - and sometimes male - bodies.

In the skit, which aired on US television, Alba is featured standing next to a photo of a man in a yellow bikini holding a cake and claims to have lost "49 pounds", and there were similar photos of Biel and Johansson.

Biel, fresh from her split last week with Justin Timberlake, exercised her comedic skills on the show.

"Hi. I'm world famous. And thanks to Jimmy K, I'm not a big fat f****** whale," the Daily Mail quoted her as telling the audience dryly.

Johansson added that before she found the 'Hottie Body Jim-Miracle diet', "I hired a ninja to slap the food out of my hand before I could eat it."

Zoe Saldana, Emily Blunt, Amanda Seyfried, Kristen Bell, Anna Farris, Kerry Washington, Marisa Miller and Heidi Klum all featured in the spoof.

Kimmel explains that the plan works by him eating four fifths of their meals, "to reduce calories by four fifths - that's 80%!"