Jennifer Garner can't diet.

The 42-year-old actress has confessed she will no longer go to ''extreme'' lengths to lose weight after spending years restricting her calorie intake to portray different characters on screen.

The brunette beauty - who played spy Sydney Bristow on the action series 'Alias' from 2001 to 2006 and superhero assassin Elektra in the eponymous 2005 film and 'Daredevil' - said: ''I mean, believe me, there's always a point in the fitting where I feel like, 'Why didn't I just try to lose four pounds and then I could wear any dress?' I just can't though. I dieted for so long in the middle of doing Alias and being a superhero, that there's something in me that can't do anything that extreme.''

The brunette beauty - who has Violet, nine, Seraphina, five, and Samuel, two, with her husband Ben Affleck - stays slim by abiding to a healthy balanced diet, although she can't resist her favourite high-calorie snack, pizza.

She explained: ''With food I'm probably good 80 percent of the time. I've found out that I cannot pass up pizza without having some. I just can't! My kids have a lot of pizza. I can't go to a kid's birthday party without having a slice.''