Story highlights Cherie Hart Steffen walked off nearly 80 pounds on her home treadmill

Steffen's mother said four words before dying: "Save money. Lose weight"

Steffen is now a certified personal trainer and hopes to inspire others to get fit

"Hey, Precious."

Cherie Hart Steffen turned toward her professor in the hall of their community college.

"What?" she asked, sure she had misheard.

"Precious -- you know, from the movie," he repeated.

The students around them started laughing. Steffen could only stare in disbelief. He had just compared her to Gabourey Sidibe 's obese character in the 2009 film

"It was like ... someone hit me with a frying pan on my head," she remembers.

Her mind flashed back to just six months before, when she had gotten a life-changing call. It was June 2009. Her mother -- her best friend in the world -- was dying. Steffen drove all night in hopes of seeing her one last time.

LaVerne Hart managed to give her youngest daughter just two pieces of advice before succumbing to the cancer that had spread throughout her body.

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"Save money. Lose weight," Steffen recites, her mother's words forever etched into her brain.

Steffen hadn't listened immediately. A herniated disk in her lower back had prevented her from working out; grief had made her turn to comfort food. In the months since her mother's death she had gained 30 to 40 pounds. But that moment with her professor was the last straw.

"This is it," she thought, as the crowd around her dissipated. "Let's do this."

A model's daughter

Steffen's older sisters were naturally thin. They took after their mother, who had been a model. Steffen did not. She grew up "husky" and steadily gained weight throughout her teenage years.

She and her mother fought constantly over her size. Hart would push her daughter to lose weight, but continued to buy junk food for the whole family.

"Bless her heart, she didn't know how to really deal with it," Steffen remembers. "I'm eating what everyone else is eating. ... None of her other children looked like me."

In desperation, Steffen tried everything from crash diets to extreme exercise to battle the bulge. At one point, she was eating fewer than 500 calories a day. She would lose weight for a short time and then put it right back on when real life won out.

Shopping was miserable. "They don't really make large clothing that's attractive," she says. "Everything just looks like a tarp." She longingly watched as her friends tried on cute clothes and went on dates. Her first kiss was postponed until college.

Eventually she carried 230 pounds on her 5-foot-3-inch frame.

Slow and steady

The humiliating "Precious" incident took place in January 2010. That night, Steffen got on her treadmill at home and walked for 10 minutes. It was rough, but she promised herself she'd do it again the next day. She was going to take the weight off no matter how long it took.

Every day she walked just a little bit longer, a little bit farther. By year's end, she had lost 30 pounds and worked her way up to a jog. She still hadn't exercised outside her house, fearing embarrassment.

She would be graduating soon with a degree in criminal justice, and thought she might make a good police officer. She started training for the fitness test, but a stress fracture in her tibia prevented her from attending tryouts at the academy.

Depression crept in. Steffen thought about what she really wanted to do. She realized she was happy with her new health routine. Could she work in the fitness industry? She did some research and came across the National Academy of Sports Medicine's certified personal training program.

Personal training is a booming job field, says academy spokesman David Van Daff.

"Everyone is aware there's an (obesity) crisis, an epidemic," he says. "People are trying a variety of different methods to improve their fitness levels, but they're not achieving success independently. They're recognizing they need a coach, a motivator, who will hold them accountable."

Personal trainers provide clients with programs to achieve their goals, Van Daff says, whether that's weight loss, muscle building or overall fitness. The National Academy of Sports Medicine certification teaches everything from basic anatomy to kinesiology to motivational techniques.

Van Daff loves to see people who have lost a significant amount of weight become trainers.

"It's helpful for somebody in this industry if they can relate to their clients from a personal perspective," he says. "If you have a personal trainer who knows what it's like to be 20 or 30 pounds overweight ... it helps in gaining (the client's) confidence."

Steffen passed her certification exam on her way to losing another 30 to 40 pounds. She designated 2012 as the year of running: She ran her first 5K in May and her first half marathon later that year. Toward the end of the year, she finally joined a gym and began to lift weights.

"(I thought) I look good in my clothes, but do I look good naked?" she says with a laugh.

Now she hits the gym five to six days a week to weight train and run. She also has cleaned up her eating habits.

Steffen eats six small meals a day that almost always include protein, whether it's chicken, tuna, Greek yogurt or fish. She has a gallon of water on her desk at work. ("I'm constantly going to the bathroom," she says.) She's given up French fries and French bread, possibly her two biggest diet downfalls, although she gives herself permission to splurge during one meal a week.

All her hard work has paid off. Steffen has lost 85 pounds and inspires others on her blog, CherieRunsThis.com

Moving on

About a year ago, Steffen ran into her old college professor, the one who had called her "Precious." She hadn't seen him since her graduation.

Like a scene from a movie, Steffen dropped an orange and it rolled across the floor. Her professor picked it up as a million sentences ran through her head.

"I had dreamed of this moment," she says. "I thought I was going to walk into his office and be like, 'Look at me now.'"

Instead she simply said, "Thank you."

"If he hadn't said that, none of this would have happened," she explains. "He still has no clue."

For now, Steffen is working as a leasing consultant at an apartment complex. But she's studying to be a fitness nutrition specialist with the National Academy of Sports Medicine and hopes to eventually get enough clients to be a personal trainer full time.

She also has her eye on a few bikini competitions, perhaps as a nod to her mother's modeling career. She imagines Hart would flip out if she saw her daughter now, and would immediately want to go shopping.

"She would love that I listened to her and took her advice," Steffen says. "She would be really proud of me because I did it the right way."