Since July, J.Lo has worked out with L.A. fitness guru Gunnar Peterson for up to two hours a day, getting in shape for last Sunday's Nautica Malibu triathlon. To train like J.Lo, follow Peterson's winning tips!

To begin: Assess your current fitness level, set up a program to shore up your weaknesses, while working individually on each triathlon event; running, swimming and biking.

Running: Work out on a treadmill and on a track.

Swimming: Do laps in pools with a kickboard and buoy drills to strengthen legs and upper body. Swim in open water as well.

Biking: Ride on bike paths, the open road and on resistance training stationary bikes.

Diet: Two hours pre-workout, eat a diet of complex carbs, oatmeal and banana and a little bit of protein. Post-workout: replenish with carbs, protein and essential fats.

Get the skinny on the shapely secrets of A-list gym rats! Pick up Gunnar Peterson's book, The Workout.