"Our society makes women feel that they should have a body of a skinny little boy," she tells PEOPLE. "We put on five pounds, and we think we're fat … It's stupid."
It's these very issues Osmond, 49, addresses in her new book, Might As Well Laugh About It Now, which also deals with life's other struggles. Publication date is next Tuesday. Says Osmond: "You have women who feel that they have to get boob jobs to be sexy. It's wrong. We're females, we have curves."
Family TeasingOsmond felt the pressure to be thin at an early age. As a pre-teen, she remembers being called "the fat sister." While hosting Donny & Marie in the late '70s, Osmond, then a petite 5'5" and 110 pounds, was told she needed to reduce. "The producers said I was an embarrassment and the show was going to be cancelled if I didn't keep food out of my fat mouth. And so, I got down to 93 pounds. I was a lollipop head."
She didn't eat for days at a time and was briefly bulimic. But when the show ended in 1979, Osmond gave up dieting. She gradually gained 40 plus pounds as a result of bad eating habits: skipping breakfast, candy bar snacks and big meals late at night.
It wasn't until her son, Stephen, now 25, expressed concern for her health that something clicked. "Stephen said, 'We need you around for our kids and your grandkids,' " recalls Osmond. "I needed to do it for my kids, but mostly I needed to do it out of self-love. [I] looked at dieting as abusive and controlling but my whole attitude changed to, 'I just want to be healthy.' "
The TurnaroundHer eating habits improved, and she began taking long walks and eventually joined NutriSystem – eventually becoming the program's celebrity spokesperson.
"It took eight years to put [the weight] on, and four months to take it off," she explains. "My metabolism shut off." That same year, she joined Dancing with the Stars and memorably fainted after a samba routine. She was eventually voted off in the finale.
Offstage, her personal life was equally dramatic. "I was going through a major divorce. My father passed away. I had a child who was struggling. He had to go into a rehab situation. I was like, 'Good grief!' " says Osmond.
Her World CrashesHer divorce from her husband of 20 years, music producer Brian Blosil, came as a bitter blow. "I had a bad marriage for 20 years and a fear of saying that it was a failure," she admits. "You have to say to yourself, 'What am I doing? Am I really taking something and trying to make it average? Does this person keep me down?' " Considering they were together for two decades, Osmond observes with a laugh, "You can't say I didn't give it a shot."
In November 2007, her son Michael, then 16, went into rehab. "Those kinds of things are really very hard for a teenager to deal with," she tells PEOPLE. "And if he ever wants to talk about it ... he will, but it has to be their choice. It's not my choice."
Now out of rehab, Michael Blosil is finishing up his last year of high school while living with his mom in Las Vegas (where she and brother Donny headline in a show at the Flamingo). "I couldn't be more proud of him," says Osmond. "He's got a 3.9 GPA in high school. He's looking at scholarships to some wonderful colleges."
Meanwhile, as Osmond faces turning 50 on Oct. 13, she jokes, "I call it the female F-word." But, she is quick to add, "I have eight beautiful children. I'm crazy busy, and I feel fantastic. So, that can be, 'Fifty – the F-word – Feel Fantastic.' I love it."