One look at Halle Berry and you'd barely believe she's in her mid-40s and is a mom to a three-year-old.

But it doesn't come natural -- behind her slim and svelte figure is a regimented diet and a multitasking fitness workout. "I always had to diet," the 5-foot-6 star has said. "It's a lifestyle for me." See below for how the 45-year-old stays in shape.

She fills up on protein
To fuel her hourlong, four-day-a week workouts with pro Nat Bardonnet, the New Year's Eve actress, who's dating Olivier Martinez, relies on protein drinks from West Hollywood's Earth Bar. Adds Bardonnet, "She also eats energy bars."

She feeds frequently
The diabetic star, mom of Nahla, eats five times a day to keep her blood sugar and metabolism up. Her meal picks: salads, fish and soups.

She makes the most of her moves
"If we can work four muscles at once, we're going to!" says Bardonnet. Their No. 1 move: quick squats combined with an arm raise. Says the pro: "You work the thighs, butt, biceps and core!"