(CNN) -- Deidre Robinson's cheeks flushed as two ride attendants tried to push her safety guard into the lock position.
At 310 pounds, Robinson knew she'd have restrictions at the theme park, but that didn't make her feel any less humiliated when she was told she couldn't ride the roller coaster with her daughter.
"There was a big guy next to me and his snapped," she said. "I thought, 'There's something wrong with that.' Obviously I was a lot bigger than he was."
The 2007 event was one of several turning points for Robinson, now 31, who was eventually inspired to join Weight Watchers and start doing Zumba, a Latin-inspired dance fitness class, in February 2009.
Less than two years later, the South Carolina native had dropped more than half her body weight -- going from a size 24 to a size 2 -- and was ready turn her healthy lifestyle into her livelihood.
"My mom always called me thick," Robinson said. "Back in the fourth grade, I remember my mom measuring my cereal ... three-fourths a cup of Cheerios."
Nobody in her family had ever battled weight problems, she said. They couldn't understand why she gained weight while eating the same things as her sister, who "to this day is just genetically thin."
By high school, she had tried just about every diet out there: from eating only chicken and rice every day for a month to "the no-carb thing."
The quick results were nice, she said, but nothing ever stuck.
Things didn't get any easier after graduation. Robinson's parents and sister, who she said she's very close with, tricked her into attending a weight intervention under the false pretense of discussing a bill.
She showed up with her boyfriend at the time, who wasn't overweight.
A few years ago, they tried again, giving Robinson a gym membership for Christmas.
"For my family to come at me like that ... they didn't intentionally try to hurt my feelings, but they were trying to wake me up," Robinson said. "They didn't know what it was like. They never had weight problems. They ate the same food (as me). They're the ones who took me to the restaurants."
Robinson said her family's well-meaning gestures did nothing to motivate her to lose weight. Rather, they made her defensive and caused tension.
Robinson's dad wasn't overtly hard on her, but she could tell he was disappointed -- "like he thought I let myself go," she said, which might have been unfair considering he had his own vice.
Just as Robinson considered eating a habit that she had little control over, her dad had smoked cigarettes since he was 20. He died at 45 in 2004 from coronary artery disease, five years before Robinson lost the weight.
"The one thing I hate the most is that my dad never got to see (me thin)," she said. "I know how proud he'd be that I got that weight off. He was always so proud of me for my job accomplishments, but he could never understand why I couldn't get that part right."
The tipping point
From what she could wear and drive to where she would sit at restaurants, Robinson's size dictated many aspects of her daily life.
"I didn't have one pair of shoes that had laces," she said. "It put me out of breath to tie them. ... I would go into a restaurant already determining in my head whether I'd need a table or booth. I couldn't drive a sports car. I literally couldn't fit behind the wheel."
And the theme park incident is just one bad memory of a too-snug safety belt.
Robinson hadn't been on an airplane in about five years when she jetted off to Miami for a work trip with her husband in 2005. She cringed as a flight attendant yelled out for someone to bring a seat belt extension over.
"In that situation, you almost feel like ... yes, you are a human being, but not only do you not fit into society because you look different and you stand out, but you literally do not fit," she said. "I wouldn't even go to a concert because the seats (were) too small. You don't want to put yourself in those situations because they're so embarrassing."
Robinson said her daughter McKenzie, who turns 10 in November, is the main reason she ultimately decided to get fit.
Up until McKenzie was 6, Robinson hadn't been in a pool with her because she didn't feel comfortable in a bathing suit. "She started asking me, 'Mom, why are you not swimming with me?' "
And as parents slid down the giant slide at the carnival with their children, Robinson waited for her daughter at the bottom.
"Why won't you go down with me?" McKenzie would ask her mom.
"I felt like I was missing out," Robinson said. "I was there. I would take her to the events, but I couldn't participate. I'm at all the events, but I'm in none of the pictures."
Thanks to Weight Watchers and Zumba DVDs, the weight started to fall off, Robinson said.
After losing 30 pounds and gaining confidence, she began taking Zumba classes at a gym. She started going a few times a week and loved it so much she continued to go every day. More than 150 pounds later, Robinson decided to open her own fitness studio in Greenville, South Carolina.
Within two months of opening Fitness Shakers in May 2011, Robinson said she quickly lost another 15 pounds -- bringing her total weight loss to 170 pounds in two years -- just from being the only instructor at the time.
"It's amazing to think I used to have these huge round chubby thick arms and now I've got this muscle definition," she said. "Pounds don't even bother me anymore. Now it's body fat percentage."
Her studio, as well as her story, now helps inspire others to be active and healthy, if the testimonials on her website are any indication: "I could never thank Dee Dee Robinson and her team enough for all they have done for me through Fitness Shakers," Jessie E. writes. "I immediately felt love, support, and acceptance walking into my first class."
"They trust me because they know where I've been," Robinson said of the members at her gym. "They know I can relate."
She now has a staff of 10 and a second location in Taylor, South Carolina, which opened in November 2011.
"I work out every day of my life," Robinson said, who also credits her fit physique to knowing what foods to eat. Salmon is one of her favorites because it's filling, yet low on the Weight Watchers' PointsPlus system.
"Do I have my one cheat day a week? Yeah," she said. "Is one cheeseburger going to make me gain weight? No."
Robinson has also noticed some other positive changes in her life since losing the weight. In addition to strengthening the bond she has with herself -- gaining confidence and happiness -- she said her relationship with her family has flourished.
"They say, 'We finally got our Dee back. Her personality is back. She's her bubbly normal self,' " Robinson said. "We're definitely closer."
She said she used to remove herself from situations, such as family cookouts, because she wasn't comfortable with her size, but now she's a lot more involved.
"I did it for me," Robinson said of losing the weight. "But maybe this whole weight loss process wasn't just for me. Never did I think I could inspire others. ... I get more gratitude from that than just knowing what I've done for myself."
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