The "Lizzy McGuire" star is eager to get back to her original size but is not taking any drastic steps for it, reported Us magazine.
"I think if you ask any pregnant mom, they're like 'I want my body back,' but it takes time. It takes nine months for your body to get that way and it's putting on that weight on purpose," said Duff.
"The second I start to get down like 'what happened to my body,' I look at my beautiful baby and I've never been more appreciative for this body that I have," she added.
But Duff said she is working hard to lose the added weight.
"I'm fine with it.
Obviously, I'm not where I want to be eventually, but I'm working hard and I'm doing everything I can to lose the weight the right way. I'm breast-feeding, so you have to be careful and not do anything too drastic," she said.