Hathaway had recently posted a message to other mothers about not being harsh on themselves post their delivery.
The first time mother says getting in shape has its emotional merits besides the physical ones, reported People magazine.
"I've started to work out - I love that feeling, I love feeling strong. I find that my workouts are really different now because I gave birth. I had been trying to fit into my jeans and it just wasn't happening, then I stopped trying - and
The 33-year-old star, whose son Jonathan Rosebanks, with husband Adam Shulman, is now 5 months old called her return to the red carpet a "funny, weird experience to have in life."
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The actress walked the red carpet at the Toronto International Film Festival to promote her movie "Colossal".
"I think shape is an ongoing thing in everybody's life. I'm not trying to recapture something that was. I'm going with what it is now," Hathaway said.
"Some things I guess are the same as they were, and other things are a little bit different. I'm just so proud of what the changes signify. So, there's no rush to do anything. I'm so happy being here.