Renee Zellweger has gained weight for 'Bridget Jones Baby'.

The 46-year-old star of the movie franchise is reportedly on a high-calorie diet of chips and liquid shakes and has piled on the pounds in order to play the titular heroine once more.

An insider told The Sun newspaper: ''She knows she can't play Bridget with her naturally skinny frame.''

Renee gained approximately two stone to play Bridget in the first two movies that were shot in 2001 and 2004.

And filming for the third in the series - based on columns written by author Helen Fielding eight years ago - began in London last month.

However, it will not follow the story of Helen's third novel 'Mad About the Boy'.

Colin Firth has reprised his role as Mark Darcy, having previously said the script would need to be right in order for him to agree to appear.

He shared: ''It would have to have somewhere to go.

''Back at the time, I said that a third one should only happen if we were telling a story about having moved into a different generation when we were all beginning to deteriorate a little bit. I think we might be ready for that moment!''