Celebrity Slimdowns of the Year
updated 01/10/2011 AT 01:00 AM EST
•originally published 01/10/2011 AT 01:00 AM EST
"Her waist is teeny-tiny," says Osbourne's trainer Sarah Hagaman, who helped the reality star, 26, whittle down to a size 2 with strength training and treadmill runs five days a week. Now on a veggie-and fish-friendly meal plan that starts with oatmeal for breakfast, Osbourne "feels a lot more confident showing her arms and waist," says Hagaman.
"I didn't expect to go as far as I did!" says the Weight Watchers spokeswoman, 29, who went from a size 16 to a 4 by learning how to eat her favorite foods like pizza in moderation and working with trainer Harley Pasternak. "I've been introduced to a whole new way of living," Hudson tells PEOPLE. "Most important, I love that I can be a role model."
She spent years publicly battling her waistline, but the country singer, 46, dropped 55 lbs.-and five dress sizes!-with the help of brain-state conditioning. "I feel really good!" she says.
At 368 lbs., "I was just shoving [food] in my mouth," says the actor, 58. Now 100 lbs. lighter after giving up alcohol and doing cardio 6 days a week, "I wear regular-joe slacks."
After calling off her engagement in August, "I had to get in dating shape," says the Millionaire Matchmaker, 49, who shed 25 lbs. with appetite suppressant Sensa. "I feel more sexual when I'm skinny."
"I was barely squeezing into a size 14, and now I'm a 6!" says the actress, 32, who lost 50 lbs. on Jenny Craig. "I'm constantly checking myself. I try not to be obsessive, but I don't ever want to go back."
The ex-dancer, 32-also known as "K-Fat"-shed 25 lbs. and "is continuing to focus on gaining back his six-pack for the new year on a strict workout regimen," says his rep.
"When I look in the mirror, I think, 'Well that's better!' " says the former Seinfeld star, 51, who dropped from 198 to 165 lbs. with the help of Jenny Craig and by working out up to five days a week.
After years of yo-yoing, the actress, 54, trimmed off 33 lbs. with Pilates and relies on the meal delivery service Freshology to maintain her diet. "My days of relapses are over," she says.
The 22-year-old royal showed off the svelte new figure she earned training for April's London Marathon. A routine of squats, boxing and jogging led to her 20-lb. loss.