Reynolds, 45, says she was "intentionally evasive" when people asked how she'd dropped 160 pounds in three years. She had gastric bypass surgery in August 2003.
She writes about her weight loss in a first-person essay in the September issue of Glamour magazine, on newsstands Aug. 7.
"Everything about me was already so public (mostly my own doing - talk about dumb!), so of course everyone wanted to know what I had done," she writes. "I was also terrified someone would have a tragic result after emulating me without making an informed decision with her doctor."
"But the complete truth is, I was scared of what people might think of me," she continues. "I was afraid to be vulnerable, and ashamed at not being able to get myself under control without this procedure."
Keeping her decision private made her a hypocrite, she says, because she had been so outspoken about her firing as co-host of ABC's "The View" last year.
Reynolds, who weighed 307 pounds at her heaviest, says her "out-of-control behavior" began around her 40th birthday in 2002. Feeling lonely, she turned to food for comfort and gained 75 pounds over the course of 17 months.
"I used to look in the mirror and take pride in my figure, but that was when I was legitimately a full-figured woman," she says. "I'd gradually gone from full-figured to morbidly obese."
Reynolds opted for surgery after a friend expressed concern about her weight. It was a success, she says, though she found she was "still consumed with the same anger, shame and insecurity as before."
Her husband, banker Al Reynolds, encouraged her to begin psychological therapy in the summer of 2005. She learned, among other things, that she "couldn't control what others thought," she says. She began to heal by talking openly about her weight loss to strangers.
(Copyright 2007 by The Associated Press. All Rights Reserved.)