Oprah Winfrey turned her weight-loss journey into a business. Here's how her health empire has evolved.

"The Oprah Effect" sent WeightWatchers' stock soaring (and tumbling).

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• Oprah Winfrey is promoting her new book, "Enough," which she cowrote with Dr. Ania Jastreboff.
• The book is the latest step in Winfrey's long journey with the business of weight loss.
• Since the '90s, Winfrey has been combining her personal health and fitness with business.

Oprah Winfrey has spent years turning her private health journey into a public conversation — and, at times, a lucrative business.