Photos: Photos: Celebrity transformations Celebrity transformations – Corey Harrison from the hit reality show "Pawn Stars" once tipped the scales at more than 400 pounds. He told People magazine he shed weight through surgery and exercise. Hide Caption 1 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – Travel Channel personality Adam Richman is proud of his more than 60-pound weight loss, but the "Man Finds Food" star's promotion of his new physique in July caused a fallout with some of his Instagram followers. Hide Caption 2 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – On April 15, Dave Chappelle was spotted in Los Angeles carrying some extra muscle. Apparently, the comedian has been spending his free time in the gym. While his physique has changed, his sense of humor hasn't; Chappelle joked with David Letterman in June that he didn't quit TV, he's just seven years late for work. Hide Caption 3 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – Rosie O'Donnell tweeted in April that she has lost almost 50 pounds since undergoing weight-loss surgery in 2013. Hide Caption 4 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – Roseanne Barr recently showed off a slimmer figure at the 2014 NBCUniversal Summer Press Day in Pasadena, California. The 61-year-old has been delighted by all the attention fans have paid to her new figure and thanked them via Twitter. Hide Caption 5 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – Lorraine Bracco of "The Sopranos" has lost 35 pounds since the HBO drama's end in 2007. She said it was the death of her parents three years ago that inspired her to make a change. Before their death, she remembers "sitting there, dividing these medications, who gets what when," she told ABC News . "It was insane. I watched and realized, 'I don't want to go like that.' ... I want to live every day the best I can be." Hide Caption 6 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – At 46, Lisa Marie Presley is feeling 16 again. Eating clean and organic has helped her to reach "the weight I was at when I was a teenager," she told People magazine . Presley, the daughter of Elvis Presley, was inspired to get fit because of her father's family history of shorter life spans. "I didn't know where I would land," she said. "So I said, 'OK, I'm going to play it safe and try to be as healthy as I can be.' " Hide Caption 7 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – Tom Arnold has lost about 90 pounds since his first child was born last year, and he was looking quite thin at this year's South by Southwest festival. He'd actually lost the same amount of weight before but regained it when he didn't maintain healthier habits. After his son was born, he knew he needed to make a lasting change. "I saw that little baby, and I thought, 'I gotta stay alive for as long as possible,' " Arnold said in January. "That's a lifelong commitment." Hide Caption 8 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – Jessica Simpson shows off a supersvelte look in a Weight Watchers ad released in February. "I was so insecure -- I couldn't even believe what I weighed," Simpson told "Good Morning America." The singer/fashion mogul says she is feeling better than ever since giving birth to her second child in June. Hide Caption 9 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – Christina Aguilera turned heads on the American Music Awards' red carpet for two years in a row. At the awards ceremony in 2013, Aguilera surprised onlookers by arriving in a skin-tight white gown with revealing cutouts, displaying a much different look than her voluptuous appearance at the 2012 event. Hide Caption 10 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – At the 2013 CMA Awards, singer Miranda Lambert revealed a slimmer physique. Apparently, her fit frame is courtesy of personal trainer Bill Crutchfield: "Hey @CrutchCamp," Lambert tweeted November 7 . "I got some compliments last night thanks to you!" Hide Caption 11 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – Chaz Bono told People in April 2013 that he had lost 60 pounds since appearing on season 13 of "Dancing With the Stars." "Diets don't work," he told the magazine. "You just have to change what you eat, and I have." Bono is pictured arriving at the GLAAD Media Awards in April 2010, left, and in April 2013. Hide Caption 12 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – There's no way Marissa Jaret Winokur could play "Hairspray's" zaftig Tracy Turnblad these days. The Tony-award winning actress dropped 60 pounds in 2012. Hide Caption 13 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – Jennie Garth slimmed down after splitting with husband Peter Facinelli in 2012. Hide Caption 14 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – Lisa Lampanelli said she underwent surgery to help her shed 80 pounds and give her a new look. Hide Caption 15 of 17

Photos: Photos: Celebrity transformations Celebrity transformations – From thong to thin: Matthew McConaughey reportedly dropped 40 pounds for a role in "The Dallas Buyers Club," and the transformation was startling on the "Magic Mike" star. Hide Caption 16 of 17