Not every bride wants a marriage proposal sprung on her on national television. Fewer still might want the wedding staged for a live audience four days later.

But Marissa Dawn LaRochelle, who married Julio Cesar Lopez on the ABC News show “GMA3: What You Need to Know” in front of 1.6 million viewers Feb. 24, had experience taking her private life public before walking down a staged aisle, cameras rolling, in the network’s Times Square TV studio.

Ms. LaRochelle, 33, is a fitness content creator known as Marissa Dawn, posting under the handle @70LbsofLife on YouTube and Instagram. In 2016, she started documenting her quest to lose weight and reclaim her health after a diagnosis of early onset diabetes. By the time the producers of “GMA3” reached out this January with an offer to talk about her journey on TV, she had dropped 140 pounds — nearly half her weight — and become a certified personal trainer and mindset coach.

Mr. Lopez, 40, knew nothing of the transformation that would one day lead them down an all-expenses paid aisle when they met.

Ms. LaRochelle and Mr. Lopez are both from San Antonio, Texas. Ms. LaRochelle moved there from Colorado as a baby with her parents, Lori and Pete LaRochelle, and brother. Mr. Lopez, an owner of the plumbing company J.C. Enriquez and Son Plumbing & Remodeling in San Antonio, was born in Nueva Rosita, a town in the state of Coahuila in northern Mexico, and raised in Texas with his parents, Julio C. and Florinda Lopez, and five siblings.

Tinder brought the couple together in September 2020. Ms. LaRochelle was steadily amassing followers for what was shaping up to be a lasting approach to better health and had recently convinced herself to start dating. Mr. Lopez, who was divorced in 2015 and has two children, ages 13 and 9, didn’t know about her social media presence but was attracted to her picture.

When they met for a first date at the Hoppy Monk, a San Antonio bar, relief swept over both. “She looked like she did in her profile, which was amazing because you never know what you’re going to get” through dating apps, he said.

[Click here to binge read this week’s featured couples.]

She was relieved he was no longer sporting the long beard he wore in some of his Tinder photos. “He was very handsome,” she said.

That night, they talked about loose skin. “I wanted to get it out there right away,” said Ms. LaRochelle, who had lost enough weight to cause her skin to loosen (she has since had the excess skin removed). “At that point, I was looking for a serious relationship, and I had encountered a few people who weren’t attracted to that.” It was a conversation Mr. Lopez could have skipped right past: “I was thinking, ‘Who cares?’” he said. “We had a connection. That’s what I cared about.”

A month later, on Halloween, he asked her to be his girlfriend. Two months after that, they quarantined together when both got Covid. “That’s the week I fell in love with Julio,” Ms. LaRochelle said. “It brought us closer.” In the spring of 2021, they moved to a new apartment together in San Antonio.

Ms. LaRochelle’s YouTube subscribers knew about him well before he proposed on the air. “I was always raving about Julio, how supportive he is and what an amazing boyfriend” he was, she said. In January, when Ms. LaRochelle told the producers of “GMA3” that they could contact him, she thought the call would be about his role in her health transformation.

But the producers had other ideas. Mr. Lopez said they got straight to the point: “They asked me if I loved Marissa, and I said, ‘Yes of course,’ and then they go, ‘We’re looking to marry one lucky couple, we could fly you in and throw the wedding for you guys,’” he said. He was onboard instantly.

For Catherine McKenzie, the show’s executive producer, the only wrinkle in the show’s first “Wedding in a Week” series came when Ms. LaRochelle paused before saying yes to Mr. Lopez’s live Feb. 20 proposal. “My heart was in my chest like, ‘Oh, God,’” she said. But Ms. LaRochelle said she just needed a beat to pull herself together before saying yes: “I was thinking, ‘I’m either going to laugh or cry or throw up,’” she said.

The show’s wedding package included a Neil Lane designed diamond engagement ring from Kay Jewelers and a trip to David’s Bridal, which gifted Ms. LaRochelle a wedding gown. Mr. Lopez was whisked to Bloomingdale’s, where he was fitted for a custom navy suit.

Their officiant, the relationship adviser DeVon Franklin, a nondenominational Christian minister and New York state marriage officiant, was part of the package, too: Days before the wedding, he got to know the couple on and off the air. “That was a surprise for us,” said Ms. LaRochelle, who had followed him online. “I couldn’t believe it.”

Just seven friends and family members, all flown to New York by ABC, were by the couple’s side when they said “I do.” As for the other 1.6 million watching from home, “This is great because I do not like stress,” Ms. LaRochelle said, adding that wedding planning may have caused some.

For Mr. Lopez, it felt even simpler than that. “Just tell me where to sign,” he said.