Robin Wright kept to an 800 calorie-a-day diet to show solidarity with her fiancé.
The 'Forrest Gump' actress had to curb her cravings for calorific treats while her husband-to-be Ben Foster got in the right shape for a role.
She explained: "My fiancé did a movie recently, playing [disgraced cyclist] Lance Armstrong, and he was on an 800 calories-a-day diet. I said, 'In solidarity, I am going to go on the diet with you,' even though I really want to go to an In-N-Out Burger."
Robin also said her 33-year-old partner has given her a new lease of life and made her feel young again.
She added: "I know I'm almost 48, but I feel like I'm 30. I feel like I've digressed and now I'm going to live my 30s again."
The actress - who was previously married to Sean Penn - also admitted she is still stunned by the prospect of getting married again.
She told America's OK! magazine: "I am in shock right now. We were talking about how we shod celebrate. We couldn't be happier."