New bodies -- fast

Steve Zim

Age: 40

Occupation: Owner of A Tighter U fitness studio in Culver City

Why he matters: Author of three quick-fix exercise books, this trainer to the stars has remapped the standard slow-but-steady approach to fitness. In fact, whether you’re getting married or just sprucing up for rehab, this miracle worker can whip you into shape in just six weeks.

In L.A., land of nanosecond gratification, Zim is the quintessential gotta-have-it-now trainer -- turning around boxers (Laila Ali), actresses (Jessica Biel) and major league baseball players (Aaron Boone) in record time. Zim’s now-you-see-it-now-you-don’t results landed him a job as the on-air fitness expert for NBC’s “Weekend Today” show and earned him spots on “Extra,” “Entertainment Tonight,” VH-1, ABC and more. His newest book, “The 30-Minute Celebrity Makeover Miracle,” is due out this month.

Zim credits his results to exercises he developed using infrared imaging to examine blood flow to muscles during conventional exercises. He found that many standard exercises don’t fully engage the muscles that they’re intended to target and altered these exercises to zero in on the targeted muscles.

For example, he says, with the shoulder press, people will drive the weight straight up over the head and drop it down. “Using an infrared camera we were able to see that when making that motion, your shoulder isn’t doing most of the work. It’s your triceps and your lat that is really pushing that weight up over your head.” Changing the mechanics of the lifting motion -- altering the angle of the lift -- he says, works the shoulder muscles more completely.

But here’s the catch: You have to be motivated. “All three parts of my plan -- aerobics, nutrition and weight training -- have to be there to get you from point A to point B,” he says.

“If you’re missing one of the three, it’s going to take longer. If you’re missing two of the three,” he says, laughing, “we may never see your goal.”

As for the notion that quick change is somehow cheating, Zim has a ready response: “No one ever joined a gym thinking, ‘Gee, I hope it takes a year to get in shape.’ They want to see results.”