PEOPLE Exclusive: Biggest Losers Then & Now

Then: The real estate investor began season 2 of the NBC reality weight-loss competition weighing 401 lbs. He only lasted six episodes as a contestant, but Thomas went on to win the at-home prize of $100,000 after losing a total of 185 lbs.

Now: The author of Lose It Fast, Lose It Forever, 46, lives diabetes-free – and has only 10 percent body fat. Though he has gained 22 lbs. – he now weighs 238 lbs. – Thomas remains dedicated to his diet and exercise routine. "Many of us contestants have struggled with food addiction," he tells PEOPLE. "I am no different. And just like any other addict, I have to be vigilant."

Then: "Prior to The Biggest Loser, food was everything to me," says Jackie, who weighed 246 lbs. before losing 89 lbs. while competing on season 5 alongside her son. Dan lasted 10 weeks longer than his mother on the ranch and lost almost half of his 310 lbs., weighing in at just 174 lbs. at the finale.

Now: Dan, 27, and Jackie, 58, head up the Biggest Loser Run/Walks and have run a total of 42½ marathons between them. "I still try and cut out all fast food," says Jackie, who has only put back on 11 lbs. from her finale weight. Dan has only put back on 10 lbs. – and released a country album in 2008.

Then: Curlee arrived on the ranch for season 11 weighing 248 lbs., and hadn't been on a date in 10 years. She may have come in second place to her sister Olivia Ward, but she walked away 120 lbs. lighter, weighing in at just 128 lbs.

Now: The former human resources coordinator, 35, has only gained back 19 lbs. and runs myfitspiration.com with her sister Olivia – and she's engaged! "I could never have talked to a man like him before the show," Curlee tells PEOPLE of her fiancé. "He would not have even recognized the old Hannah because I was so unhappy and bitter about life."

Then: The professional opera singer weighed 261 lbs. before she got down to 132 lbs. for the season 11 finale, where she beat out her sister Hannah Curlee for the title of The Biggest Loser.

Now: Ward, 38, weighs 145 lbs. and is a SoulCycle instructor and certified personal trainer. "I had no idea when I stepped on to a weight loss show that not only would I shed pounds, but that I would gain a life I never knew was even possible," says Ward, who just celebrated 16 years of marriage with her husband Ben.

Then: "The Biggest Loser opened me up to see that I had so much more life in me than I was living," says Jacobs, who weighed 400 lbs. before losing 181 lbs. and making it to season 11's final four.

Now: "Our family [has lost] a collective 435 lbs. since our finale," Jacobs, 57, proudly shares (he's gained just 6 lbs. since the show). He and daughter Jennifer, also an alum, "have coached and supported our extended family to get healthy, as well. My new mindset is that 'I'm living the rest of my life as the best of my life!'"

Then: Jay's daughter came to The Biggest Loser with him, weighing 278 lbs. She eventually lost 114 lbs., weighing in at 164 lbs. at the finale. "The experience showed me how to release my fears and tap into my inner strength," she says.

Now: The 31-year-old health coach, who's gained 12 lbs. since her season, helps others reach their weight-loss goals. "Paying it forward as a health coach has been one of the greatest motivators to staying healthy," she shares.

Then: Oguntala began season 15 weighing 319 lbs., but after losing a record-breaking 54.86 percent of her body weight, the advertising brand strategist weighed in at at 144 lbs. at the finale and scored the at-home prize of $100,000.

Now: Though Oguntala, 42, has increased her carb intake ("to improve my running performance," she explains), she has only gained 21 lbs. since her finale weigh-in. "I have a sharper mind and body and so much more confidence," says Oguntala, who is set to walk down the aisle on Nov. 21.

Then: Though he only lost 25 lbs. during his two weeks on the ranch, Hayes ended season 7 with a record-breaking at-home weight-loss of 151 lbs., which took him from 369 lbs. to 192 lbs.

Now: "I no longer have diabetes, gout, sleep apnea or glaucoma," says Hayes, 69, who works as a personal trainer at the Biggest Loser resort in Chicago with wife Estella, also a Biggest Loser alum. "I have tried to make food into a fuel and not a pleasure like before The Biggest Loser," he adds, citing just a 22-lb. gain since the show's end.

Then: Jerry's wife lasted just one week on the ranch thanks to a game-changing twist, but was still able to lose 83 lbs., weighing in at 159 lbs. at the season 7 finale. "My sister passed away two years before we got on the show," she says. "She was 400 lbs. and coded in the ER and died. Jillian helped me mourn and then move on and make my journey about me and Jerry."

Now: Weighing 173 lbs., Hayes works with her husband of 48 years at the Biggest Loser Chicago resort and enjoys life with her five grandchildren. "We try to motivate as many people as we can to help them – and keep us on track," the 69-year-old says.

Then: Hickerson weighed 426 lbs. before becoming a final four contestant on season 12 and whittling down to 242 lbs. "The doctors said I was two years away from death," Hickerson tells PEOPLE of life before The Biggest Loser. "It saved my life."

Now: Having lost an additional 4 lbs. since the finale, Hickerson, 31, says he recently signed a record deal and opened the "shabby chic" furniture store The Faded Farmhouse with his wife. "I cook all my weekly meals on Sunday night so I'm prepared to succeed through each week," says Hickerson, who is also training for his first bodybuilding competition.

Then: The season 14 winner began her weight-loss journey at 258 lbs. before becoming known as "the girl on fire" and weighing in at 137 lbs. at the finale.

Now: The former marketing coordinator, 27, is a certified yoga instructor and opened up her own studio. "I do my best to eat clean: no processed foods or preservatives. I'm mindful of my portions and of course enjoy the occasional treat," says Allen, who weighs 155 lbs. and is training for a 36K run up a mountain in Costa Rica this November.

Then: Though she was eliminated one week before the season 15 finale, Winfield still went on to lose a total of 87 lbs. and eventually weigh in at 175 lbs.

Now: "I've learned to love myself and others unconditionally," says Winfield, 42, who weighs 182 lbs. and started her own line of healthier soul food, LivinSoul. "I plan my workouts and meals with the same dedication and focus as I did with my executive boardroom meetings."