People.com: Lisa Rinna's secret to looking fabulous in her upcoming May spread in Playboy? Skipping the gym.

"This was really hard for me because being 45 years old and posing for Playboy, you want to amp it up," Rinna told PEOPLE at Tuesday's Room 23 book launch hosted by Diana Jenkins and Neuro Brands.

Rinna explains she received direct orders from Playboy photographer Deborah Anderson, who also shot Rinna for the Room 23 book, which was created by Malibu businesswoman and activist Diana Jenkins to benefit the UCLA Sanela Diana Jenkins International Justice Clinic.

"She said, 'I do not want you long and sinewy and angular and muscular. I want you soft,' " says Rinna.

What did her biggest fan think of her photos?

"Unbelievable!" says hubby Harry Hamlin. "They're absolutely awesome!"

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