Marie Osmond is one busy single mom. Between shows with brother Donny Osmond at the Flamingo in Vegas and looking after eight kids, now she's shooting a new commercial for NutriSystem. Is there room for romance? ET's Jann Carl gets the goods behind the scenes!

"I was doing 'Dancing with the Stars,' and I guess the press found out I was on NutriSystem, and that's how the whole [commercial] thing happened," explains Marie, who dropped 40 pounds on the plan, with a little help from exercise and, of course, singing and dancing!

"Heart disease runs in my family, and I was feeling every symptom, and so it really made me go, 'Okay, how do I do this quick? How do I do this smart? How do I be healthy? I don't want to be skinny, I want to be healthy,'" she continues. "And so I looked at all the options and, actually, I found NutriSystem. They didn't find me."

"It's really fun to be with Donny again," says Marie about performing with her brother on stage again after so many years, but she acknowledges that it was a big life change to move to Las Vegas.

"The biggest thing for moms, and I know that everybody out there will agree, is that if your family isn't taken care of, if your kids aren't happy … you're not happy," she tells Jann. "And so it was really a methodical pacing to get it all put into play, and it's all starting to work now and gel, so it feels really good."

So, is there any room for romance in her busy schedule -- or marriage for the third time?

"It would have to be a miracle," she laughs. "I've been damaged, and when you go through two [marriages] -- and if you ask any woman who's been through it -- you give your heart so much, and then you're kind of like, oof. It's that fear of letting somebody in again."

As for dating, she says, "I've had wonderful offers by many, many sweet people. And I don't mind going to dinner and things like that, but the peace comes from knowing my kids are okay first."

Watch ET for more with Marie!