What’s Christina Milian’s vice? Junk food. “Cheetos, Oreos, everything terrible!” says the 5-foot-2 Christina. But her unbridled food intake gave her pause last year when she suffered an allergy attack after eating radishes.

“I had hives everywhere for a month! I thought, I can’t control this, but I can control the way I look and be fit.” For diet help, Milian drew on experience. “When I was 16, I was chunky and I lost about 25 pounds,” she says.

“My friend Jessica Biel taught me about healthy eating. We would have beans and apples as a snack.”

Using the same lessons as an adult, the trainer-free Milian replaced fried rice and lasagna with salmon, turkey bacon and egg white omelets and began a six-days-a-week regimen of running on the treadmill for 30 minutes, followed by squats, lunges and situps.

“I wanted to tighten up,” says Milian, who dropped a size and 18 pounds. “I definitely reached my goal.” Her reward? Dre, her record producer boyfriend, bought her a sexy pair of Diesel jeans. “They show off my butt!” she says. [via]