Movie star Toni Collette has vowed to think twice about dieting for movie roles after having to gain and lose 25 pounds (11.3 kilograms) while shooting her new film In Her Shoes.

The Australian actress, who gained 43 pounds (19.5 kilograms) for her role in Muriel's Wedding, started the new film playing a chubby depressive and had to lose the bulk as her character recovered towards the end of the film.

She says, "I vowed to the high heavens that I would never put on weight again for a movie, but (director) Curtis Hanson has this way of getting what he wants and I ended up putting on 25 pounds to play the part.

"Then, once ROSE, my character, becomes a happier person it affects her physically so I then had to lose the weight through a rigid diet and exercise programme during the middle of shooting.

"I don't think I'll be doing this weight see-saw thing again."