Aniston, 45, had earlier confessed that like any bride-to-be she would lose some weight before her marriage. reported Ok! magazine.
"She doesn't think she's overweight by any means. But she's always said that she feels most confident when she looks a certain way. And there's no doubt she'll want to have that same feeling on her wedding day," a source said.
After meeting Theroux, the 'Friends' star has allegedly put on some weight as the couple are often involved in dinning.
"His idea of fun is going out to great restaurants and trying out amazing food with her. And if that leads to her gaining a little weight, he's not going to complain.. Justin thinks Jen looks absolutely perfect the way she is. He likes her curvier, with a little meat on her," the source added.