"I hear there's been a lot of pictures of me surfing. I cringe at the thought of them," Macpherson told PEOPLE at Sunday's Golden Globe awards.
"Listen, have fun," she says of her first workout rule. "Do lots of sport. Don't worry about your silhouette, worry about how you feel. That's what I say to myself: 'How do I feel today?' "
Macpherson focuses on sports she can do alone, since she travels so much. "I do sport because I love it," she says. "I'm Australian, and I have an outdoor life. And maybe that's what people see. I surf, I snow ski, I water ski, I ride a horse, I hike, I paddleboard."
She also doesn't obsess over her diet. "I had chicken fingers and fries at lunch," she said on Sunday. "I was so hungry. You can check my room service bill."
Macpherson, who will host a new reality show, Fashion Star, on NBC beginning March 13, presented an award with Ashton Kutcher at Sunday's show – and said it was the highlight of her night.
"He's a wonderful person," she said. "He was very supportive. I was very nervous because it's my first time at the Golden Globes."
The pairing made sense. "We're the same height," Macpherson said with a laugh. "He was the only bloke I could present with."
Reporting by MELODY CHIU