From her early years growing up on Long Island, New York, she got her first whiff of how bold decisions can pay off. She moved to Manhattan and landed a job in the apparel business knowing nothing about retail. From one job to the next, she ultimately worked her way to executive positions at Tommy Hilfiger, Ralph Lauren, Nike and Home Shopping Network. Everywhere she went, she reinvented and rebranded legacy companies turning them into success stories and gaining a reputation as a powerful change agent.

Now Grossman is transforming the company once known as Weight Watchers. As the new CEO she has rebranded the 55-year old weight loss leader into a company focused on health and wellness, renaming it “WW International”.

“I love transformation. I love legacy brands,” says Grossman. “I love creating meaning for people whether they be employees, consumers, or partners. And this was such an opportunity at this point in my career to really have a great impact.”

But what really convinced Grossman to take the top job at Weight Watchers was talking with Oprah Winfrey, who is not only the company’s spokesperson and ambassador, but also a board member and one of its largest shareholders.

“Her belief was certainly validation,” says Grossman about her first conversation with Winfrey. “The belief that we could transform not just ourselves but help transform people’s lives. And that was very meaningful to me.”

Grossman has been constantly preaching and repeating that message to WW’s 18,000 employees and to the company’s 4.5 million subscribers.

“Transformation is not easy,” she tells Fortune. “But in today’s world, if you’re not moving and you’re not moving forward, you’re not agile, and you’re not evolving, you’re going to be left behind.”

And Grossman is not the type of leader who will allow that to happen to her, or to WW.

Watch the video above for more from my interview with Grossman.