"Staying fit is something I'm really passionate about," Pratt, who changed her last name from Montag after marrying Spencer Pratt, tells PEOPLE. "I work out with a strength-and-conditioning coach 90 minutes a day, five days a week"
Now she's planning to share the specifics of her routine of "full-body, intense resistance exercises" in a new downloadable workout series developed with trainer Chad Waterbury.
The series features full-body conditioning exercises executed as rapidly as possible, "so you burn fat faster," says Waterbury, who does both light and heavy weights (think 75-lb. kettlebells!) with Pratt to give her body "a hard look with a feminine shape."
The Heidi Workout will also offer nutritional advice based on guidelines Waterbury gave to the 22-year-old TV star. She avoids all "white" foods like carbs, but fills up instead on lean meats including grass-fed beef – ("Heidi loves steak!" Waterbury says) – and green vegetables, apples and berries. "Heidi has a really healthy appetite," Waterbury adds. "There's no way she is going to deprive herself."
Andy Johnstone / Pacific Coast News
And a major confidence-booster. "She loves showing off her body now," says Waterbury. "She called me from her Playboy shoot and was so excited. The photographers were raving about her."