KELLY PRESTON, 51
"You are as old as you feel and I feel like I'm 25," Preston told PEOPLE last year, announcing she'd lost nearly 50 lbs. since welcoming son Benjamin in 2010. Her secret? "I'm running after a 2-year-old and keeping up completely! Ben runs around and three, four, five times a day we go outside and find frogs, millipedes and lizards. It's always, 'Mama, get it! Mama, get it!'"