The 42-year-old personal trainer proposed to Rhoades on the Season 1 finale of her E! reality series, "Just Jillian," which aired Tuesday.
Michaels brought Rhoades to a private theater where she showed a video montage of their years together. The video included photos of their many adventures and their two children, daughter Lukensia and son Phoenix.
"In a world where it's tough to connect, one woman found that someone special and came to discover that where there's love there's hope, happiness, adventure and endless possibilities," Michaels wrote.
"We were a great couple but better as a family I have been thinking a lot and while so much of life is unknown, there is one thing I know for sure. I want to be with you for better, for worse, in sickness, and in health, for the rest of my days."
Michaels and Rhoades have been together since 2009 and adopted Lukensia from Haiti in May 2012. Rhoades gave birth to Phoenix the same month.
"Heidi is the perfect person for me," Michaels reflected. "The only place where there's like a solace and a respite, a save-haven, is with my family. And Heidi is the nucleus of that family. She's the glue that really holds everything together."
Michaels thanked fans for their well wishes after the episode aired and revealed the proposal actually took place "about 4 months ago." The personal trainer is best known for her work with "The Biggest Loser," which she exited after Season 15.
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