The 'Mystery Girls' star admits she piled on the pounds after she broke up with the 40-year-old actor - with whom she has three children Luca, 16, Lola, 11, and Fiona, seven - in 2012.
She said: ''Yeah [I put on weight after the split] I was super depressed. I had to lose the weight when I was even considering coming back to Hollywood and needing to make a living-- knowing what I do is based on how I look, seeing pictures and going, 'Whoa, nobody is going to hire that to be on TV'.''
Jennie and Peter divorced last year and, although she found it a difficult and emotional process, she claims the break-up has given her time to work on herself.
She told FOX411: ''That is the one good thing about divorce: I have time to actually be with myself, take better care of myself when my girls are with their dad.''
Meanwhile, the blonde beauty, 41, insists she's not dating anyone at the moment, but she hasn't ruled out having more children with someone in the future.
She explained: ''If the right situation arose yeah, sure [I'd love to have more kids]. I love children. My girls are very close. They fight constantly. They kill each other every day but they love each other.''
The actress spoke about raising her 11 year old daughter Matilda in the wake of Heath Ledger's death eight years ago.