Subway CEO Suzanne Greco's plan to freshen up the world's largest restaurant chain

The world's largest restaurant chain is getting a makeover. Subway grew from one Connecticut storefront to nearly 45,000 locations in more than 100 countries, but the company shrank for the first time in 2016. Now, it hopes a new look will help jump-start the 50-year-old brand.

"CBS This Morning" co-host Norah O'Donnell went behind the counter with Subway CEO and lifelong employee Suzanne Greco. In her first TV interview, she spoke about taking over the company started by her big brother, and the struggles of staying competitive in the fast food industry.

Today, the Subway experience is familiar around the world, but when 17-year-old Fred DeLuca opened Pete's Super Submarines in 1965, it was a family affair.

"We came from a very modest family and the idea to open that first sandwich shop was really for Fred, my brother, to generate money to pay for his college because we didn't have any money," Greco said.

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Greco started working in a Subway at the age of seven.

"I was so intrigued with this idea that 'we own a business' this was like a big deal to me, and I just wanted to be a part of it," Greco said.

In 1974, DeLuca began recruiting outside owners to buy Subway franchises and by 1990, there were 5,000. But Subway's founding family received devastating news in 2013. DeLuca had leukemia, and he named his little sister Suzanne Greco as his successor.

"Those who've worked for their family will attest to the fact that they're hardest on you. Never did he want people to think that he handed something to me or that I didn't earn it," Greco said. "And, you know, when we got toward the end of this, you know, he said, 'You're ready. I want you to carry on the legacy.'"

Surprisingly, Subway has more stores worldwide than McDonald's – almost 45,000.

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Suzanne Greco and Fred DeLuca

"We are the largest restaurant chain out there, but it's really about that one sandwich. That one sandwich, that one customer. And serving, you know, seven and a half million sandwiches a day," she said. 

Greco took control in the midst of a public relations crisis when national spokesman Jared Fogle was arrested on child pornography charges. The following year, rivals grew, while Subway's sales declined and for the first time the company closed more locations in the U.S. than it opened.

Of what she believes caused the decline in sales, Greco said, "There's a lot of disruption so we were the ones that started with this fresh revolution. That's how we started, and that's who we're going to be, that's who we are. But many brands are starting to do that. And that is what customers want," Greco said. "Consumers' ideas about food and their ideas about restaurants and service have evolved and being the size that we are it's not as simple to make a change, but we are making rapid changes."

Those changes include renovated storefronts, highlighting Subway's use of fresh produce, kiosks where customers can place orders, and a mobile app where loyalty is rewarded.

"Do you feel like you have to reinvent Subway for the 21st century?" O'Donnell asked.

"Fresh, nutritious, customized food at an affordable price, was relevant 50 years ago. That is still relevant today, but we do have to evolve because fresh has a different meaning than it had 20 years ago," Greco said.

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Suzanne Greco

CBS News

She pointed to Subway's partnership with farms across the country that allow it to move produce from field to sandwich in a matter of days. Still, she says the key to Subway's success resides behind the counter.

"I love it. I love making sandwiches. It taught me so much," Greco said.

Facing a rapidly-changing industry, Greco believes that fulfilling her brother's goal of 100,000 locations remains within reach.

"The idea of being able to provide this fresh, nutritious, customized sandwich and at an affordable price, I feel that yes, every community should have that available to them," Greco said.

Of the top ten restaurant chains in America, Subway is the only one with a female CEO.

"I'm extremely proud to be leading this brand. It's really, really exciting for me. I don't think that there's anybody out there that knows more about this brand or loves this brand more than I do."