Preparing to make her ring debut in a charity boxing match, Kristin Callahan was sorting through a list of nonprofit organizations, trying to decide which one she should adopt as the beneficiary of her fundraising efforts.

Callahan decided she needed help, so she sent out a group message to her numerous cousins, known in the family as the “Cuzz Buzz,” to ask if any knew of a worthy organization.

A cousin from New Jersey suggested The Marisa Tufaro Foundation. A Massachusetts transplant from Long Island, Callahan had never heard of the nonprofit. Her cousin knew Marisa Tufaro’s mother, so Callahan sifted through the list and clicked on the foundation’s website.

The nonprofit’s namesake had died at the age of 13 from a rare form of cancer following a long battle during which she survived six open-heart surgeries and a heart transplant.

“Her name immediately hit home because my mom always loved the name Marisa,” Callahan said. “She would have named my brother Doug, a year younger than me, that name if he was a girl. My mom loved horses, and so did Marisa. But the clincher was that Marisa’s birthday is July 30. My mom’s is July 29. When I read that it gave me total chills. I started bawling and was like, ‘Oh my God.’ I’m not a person who believes in signs, but this is just … yes!”

Callahan, 47, lost her mother to cancer 12 years ago. A personal trainer who resides in the Boston suburb of West Roxbury, she was on a mission to fight against cancer by, well, fighting.

On Sept. 29, Callahan took part in the ninth annual Haymakers for Hope “Belles of The Brawl,” a women’s boxing charity event with a dozen bouts on the card at the MGM Music Hall at Fenway in Boston.

Since its inception in 2011, Haymakers for Hope has raised more than $20 million for cancer research, awareness, survivorship, and care through organized charitable boxing events.

Callahan took up boxing last December, saying, “Something about it spoke to me. I wanted to learn the sport and the skill of it. I never thought I wanted to do a fight, but the more sparring I did the more I got excited about it. I learned so much about myself in this process, like the fact I could take a punch to the head, get my bell rung and keep going. There is such a requirement of body, mind, and soul to the sport; something really beautiful that asks a lot of your entire person.”

Approached earlier in the summer about taking part in the event, Callahan initially downplayed the idea. After all, she had a 10K race approaching in September.

In late August, however, one of the boxers withdrew due to an injury and Callahan was asked to fill in.

“I knew it was an awesome event,’’ she said. “Everyone else had already been training for a few months, but I knew I’d be mad at myself if I didn’t do it. The next day I was told what I had to do, cut 10 pounds and have an intense schedule. I woke up the next day and started freaking out! ‘What have I just gotten myself into?’

“I went to the Brawl website of my opponent (Nicole Gonsalves), clicked on her bio and read her story. She had lost her husband to cancer a few years ago and was in her early forties when it happened. Obviously, I started crying.

“So now I know I don’t even care if I lose to her. I have to do this. I started training with a professional boxing coach and it happened! I didn’t win, but I didn’t get my butt kicked,’’ she said with a laugh. “It was a good fight. I had a lot of really good right hooks. I was really proud of the way I fought. I showed up!”

All 5-foot-5, 145 pounds of her.

Through her three-round boxing match, Callahan raised more than $2,600 for The Marisa Tufaro Foundation, generating funds through her network of people via social media, texts and emails.

“The key is providing the links for easy access to the information to donate,” she said. “I think having a big family definitely helped. It was really cool getting all the messages of support and seeing who donated. Unfortunately, almost everyone knew someone who has battled cancer.’’

The Marisa Tufaro Foundation, since its inception five years ago, has donated more than a quarter million dollars to fulfill its mission of assisting pediatric patients and underserved children throughout the greater Middlesex County (NJ) area.

The non-profit has spearheaded multiple community initiatives resulting in the collection of thousands of toys, nonperishable food items, winter coats, baby supplies and other items for donation upon which it has placed to monetary value.

The foundation has also awarded $26,500 in college academic scholarships to 38 high school graduates, and an additional 13 scholarships for middle school and elementary school students to attend a weeklong summer art camp at Rutgers University’s Zimmerli Art Museum.

Callahan played some soccer and took part in gymnastics as a youngster, and later took up tennis. But she had never laced up a pair of boxing gloves until last year.

“I was always active but was also always the chubby kid who wasn’t good at things,” Callahan said. “My dad, who’s a cancer survivor, started running and every day asked (all five siblings), ‘Who wants to go running?’ One day I was like, ‘Yeah, I’ll go.’ So we started running together. I started eating better and lost weight. There were a lot of ups and down.”

Callahan attended Boston University, where she played some intramural soccer and was a soccer referee, “which was hilarious,” she said, “but I never considered myself good at any of that stuff.’’

Matching brains with her newfound brawn, Callahan has been a freelance copy editor since 2009 for a variety of nuclear and particle physics journals. She was certified as a physical trainer in 2015.

“We collaborate to find things that work for them and their goals,’’ Callahan said about her job with clients in the gym. “I also help guide them and teach them ways to integrate health, fitness and nutrition into their own lives. There’s no one answer. The type of personal training I do is to help create a lifelong habit that grows and evolves as the individual does. And have a fun time doing it. There’s something about doing something that’s more than you; doing something outside of yourself that benefits others. It’s not just yourself having that connection.

“On the day of the event,’’ Callahan said, “with all the other fighters and all the volunteers, when you realize you’re part of something that is so much bigger than you, that you can make an impact it’s almost indescribable. I can’t even find the words. It makes you feel like life is worth living.”

Callahan’s inspiration in the ring and in life has been her mother, Carole, who was diagnosed in September of 2009 and died the following June.

“I went back home for Mother’s Day, and she wanted me and my sister to sort through her jewelry,” Callahan said. “She had worked at Tiffany’s. I was still in denial that she was going to die. A month later doctors told her there was nothing else they could do. It was a weird thing that it helped me because I knew she didn’t want to be a sick person. It gives you an opportunity to say good-bye and to say everything you’ve wanted to say. My grandmother passed away suddenly from a heart attack. With that, you don’t get the opportunity.

“There’s sort of a freedom knowing what’s going to happen,’’ she offered. “The thing I regret was not going through her jewelry. I wish I had done that with her.

“You need to take in the moments,’’ she said. “Whether it’s just sitting together or if you want to do something like (sorting jewelry). Just seize the moment. And that goes for every day, whether you’re battling cancer or not. Life is short. Just do it.”

That is just what she did last month in the ring, despite her hesitancy.

“I’m so glad I did it,” Callahan said. “It’s brought me so much joy and love into my life. And who would know that getting punched in the face, that this would be the outcome?

“Just do the things that scare us,” she said, “because those are the things we need to do.”