The 25-year-old actress-and-singer gave birth to her first child Luca nine months ago and has gotten back to her pre-pregnancy weight through a combination of exercises but boxing has proven to be the most successful in shifting the pounds.
Her trainer Gabe Johns said: "Her main love is boxing. We skip rope and run boxing intervals with one minute of rest between. It`s important to find an activity you love so that you look forward to the workout.
"Hilary comes ready to train with a smile on her face because she loves the challenge of something new.
"She was really looking for a workout that was challenging and to be pushed to the limits of what she could do physically."
Diet is also important to Hilary - who is married to retired ice hockey player Mike Comrie - and she eats a menu heavy in kale and lean meat and fish to maintain he fabulous figure.
Gabe added to the new US issue of OK! magazine: "Hilary has been very conscious of maintaining a nutrient rich, healthy diet. She eats leafy greens such as kale or spinach along with lean proteins such as salmon or chicken."