Nancy reads her letter to Oprah.

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After losing more than 500 pounds and cutting back on her three-pack-a-day smoking habit, Nancy says she feels good. "It's amazing. My knees are fine. My heart's fine," she says. "I'm an iron horse. What can I say?"

Though Nancy can't identify a painful experience that triggered her compulsive eating habits, she does remember her mother exhibiting similar behavior. "I used to watch my mother eat food when I was a little girl. When something went wrong, she would go into the kitchen," she says. "Maybe that's something that I learnedyou comfort yourself. Food's a comfort, but it's terrible the minute after you [eat] it."

Now, Nancy says she's in complete control of her eating. "I don't know how to explain it except that I really don't struggle to stay away from four pieces of cheesecake anymore," she says. "I don't deny myself oneI can have one. I just don't want four anymore."

In a letter Nancy wrote to The Oprah Winfrey Show, she reveals her new outlook on life. "I smile all the time now. Some think I'm crazy," she reads. "But I know a secret. There will always be a sunrise and a second chance if you believe. I believe. I believe in me."

Read Nancy's entire letter about her weight loss journey.
As a reminder, always consult your doctor for medical advice and treatment before starting any program.