Rebecca Romijn has dropped nearly 60 pounds after welcoming twins Dolly and Charlie in December -- without a workout plan.
"I think within the first three weeks, I took off, like, 35 pounds without doing anything!" she tells Extra.
Chasing her four-month-old twins has kept her too busy to hit the gym, anyway.
"I haven't been able to work out that much because I have twins," says the Ugly Betty star. "It's impossible to get back into a regular schedule."
"Breastfeeding is the very best diet I've been on. It's amazing," she says. "It's like you have to eat 5,000 extra calories a day or you can't produce enough food for them. So, that's been fun as well."
But she admits she isn't completely back to her pre-baby bod.
"I'm not pretending to be back to the shape I was in beforehand anyway. I still have a ways to goWe've got Spanx underneath almost everything" she says.
Romijn -- currently filming The Love Child in Canada -- says being a working mother is tough "for a number of reasons."
"Our hours have been really late and we're working outside of Toronto in Hamilton, which is about an hour away [from where husband Jerry O'Connell and the twins are staying] -- and I am still nursing [the babies] around the clock," she says. "So, we have to do a lot of milk runs."
O'Connell has been "like, totally on diaper duty," Romijn continues. "He's so awesome. I think he's having a really good time also."
Romijn says her twins are "really smiley and not fussy. For four months old, it's supposed to be really difficult, but I have to say, it's just fun."