The former center midfielder underwent surgery on the chronically plagued arthritic knee only months before her 2011 graduation.
Hallihan knew her knees would never be the same, and returning to the soccer field was completely out of the question.
"Being an athlete, I never had to worry about diet or exercise," said Hallihan, who put on 50 pounds and "hit rock bottom" in December 2013 while shopping for a New Year's Eve party.
The size 11 jeans didn't fit, and Hallihan was "too embarrassed, depressed and self-conscious" to enjoy her night out.
Instead, she stayed home researching fitness tips. Her journey started the following day.
Eating three meals and three snacks per day, Hallihan allowed herself no "cheat meals" until her 21st birthday and and vowed to spend an hour a day at the gym.
She met her goal, celebrated with a short stack of pancakes and then went back to business. But this time, she had a new goal: to inspire others to do the same.
“If you come up with a solid plan, [weight loss] is possible,” said Hallihan, currently a personal trainer at LA Fitness in her hometown. "You don't see changes day-to-day — you just have to stick to it."
After dropping 45 pounds, Hallihan picked up weights and began training to become a National Physique Committee competitor. She took home fourth place in her first show October 2015.
“I wasn’t expecting a win,” Hallihan said. “Getting up on the stage was a win [in itself].”
Then, she brought home second place out of 40 competitors in her second show.
Early morning cardio and lifts — along with a strict eating regimen — was a challenge Hallihan, but ultimately paid dividends, she said: "it was worth it."
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