On this Easter morning, Sara Harper has found a new life.

In five years, she has shed more than half of her one-time 300 pounds, completed a marathon and two half-marathons and plans to run in the Boston Marathon April 16.

“I feel like I have a new life,” Harper said a few days ago, hours after completing a 20-mile training run. “I’m stronger. I am who I always have been, but I’m able to let that come out more. I have confidence in who I am and what I’ve accomplished.”

The 34-year-old said she feels like she’s 25, and her glow shows it.

“I know it sounds trite, but it’s not because of something that’s happened or some outward thing. I’m happy because of me, because of what I’ve done,” she said.

A Vicksburg native, the daughter of Jack and Karen Faulk Williams and Ken and Terri Harper, she attended St. Francis Xavier Elementary School and Vicksburg High School, graduating in 1995. She earned a bachelor’s and master’s at Mississippi College.

“All her life she was pretty much a couch potato, not an active person,” Karen Williams said. “She struggled with her weight all her life.”

“I always wanted to be like everybody else,” Harper said. “I just wasn’t.”

About five years ago, Harper underwent gastric banding surgery, traveling to Mexico for the operation at a fraction of its cost in the U.S. She lost about 80 pounds, she said, but the band eroded, causing serious problems, and she ended up getting sick. In May 2010, she had the band removed.

Five months later, Harper had gained back about 40 pounds when she ran into her friend Bradley House and Bradley’s husband, Patrick, at a local store. Patrick House was in the competition for the 2011 season of “Biggest Loser,” which he ultimately won, and Harper was struck by how much weight both he and Bradley had already shed.

“I went home and emailed Bradley, asking, ‘What did you do?’” Harper said. They told her, count calories and exercise.

So she did.

“She just got her mind right,” said Karen Williams. “She began eating well and exercising. She did it the old-fashioned way — nothing more than hard work and eating healthy.”

“What’s her secret?” said Wayne Scott, a fitness instructor at Vicksburg’s W.K. Purks Y, who has worked with both Patrick House and Sara Harper. “Willpower. Old-fashioned work. When she comes in to the gym to work she gives 110 percent.”

“I changed everything I ate, and when I ate, and how much I ate,” Harper said. She focused on whole grains, lean proteins, fruits and vegetables, but also ate a Twinkie when she just had to have a Twinkie. Laughing, she said she just didn’t eat a whole box of Twinkies.

Harper also joined the Y, privately hired Scott as a personal trainer and got into Marathon Makeover, the 40-week program that trains runners to complete a full or half-marathon.

“Marathon Makeover played as much a part of this as anything,” said Scott. “She had a hard time running five yards at first, let alone 26 miles.”

“When she started running and changed her eating habits, she was really able to change and finally lose weight,” said Jack Williams.

Harper ran the Madison marathon Oct. 15. “It was terrible,” she said. She hadn’t trained enough — the longest distance she’d covered in practice was 14 miles — and her knees were acting up.

She got up the next morning, sore and blistered, and told herself, “I am never doing this again.”

But a day later she went to the Y to stretch her legs on the treadmill and had another chance encounter with Patrick House.

“He said, ‘If you want to run Boston I can probably get you on the team,’” she said. “I thought about it for a little while and said, ‘I’m in.’

“I mean, it’s the Boston Marathon,” she continued. “It’s the Super Bowl of marathons. You just don’t turn down the Boston Marathon, especially when you’ve been where I’ve been. Five years ago I weighed 300 pounds.”

“The team” to which House referred is a group that’ll run with official Boston Athletic Association numbers but do not have to meet qualifying times because they are raising money for charity. Harper has raised more than $4,000 for the American Liver Foundation, she said.

Since running into the Houses 18 months ago Harper has lost 123 pounds — in addition to the 40 she kept off after the gastric band surgery — and faced up to mental as well as physical challenges, sticking with it when she felt like giving up.

Scott said she’s a new person — physically, spiritually and mentally.

“It’s so easy to just keep your habits,” he said. “Once she learned that, she worked to change her lifestyle and it became easier for her both to lose her weight and build her self-confidence.”

“You have to separate yourself from what’s making you feel like you want to stop working at it,” she said. “It’s overcoming the mental battle. That’s what took me (so many) years to do.”

Professionally, Harper has gone from inspiring little kids to grown women.

After teaching kindergarten and second grade at Beechwood Elementary for five years, then first grade at Sherman Avenue for part of this year, she resigned in December and has taken a position as a gym floor instructor at Fitness Lady in Ridgeland. After Boston, Harper hopes to earn her personal training and aerobics certifications.

“I am so proud of her,” said Scott. “It will help her in the long run because it will help keep her focused, but she is also going to inspire other people. The people who have seen what she’s done just say, ‘Wow.’”

“I get chills when I think about Sara and her ability to help other people,” Karen Williams said. “People can relate to Sara because she has been through it.”

“I feel like God just led me somewhere else,” said Harper. “I think everything that’s happened to me is part of God’s plan. He has better things in store for me.”