Bradley Bayou's red-carpet creations for such curvy celebs as Queen Latifah and Oprah Winfrey built him a fashion empire and earned him the nickname "The Man for All Sizes." Bayou, a vocal opponent of skeletal models, celebrates the beauty of all women in his book The Science of Sexy, out this month. Yet in 2004 his daughter Alexis, then 24, made a startling revelation: Since age 18, she had battled bulimia and an addiction to laxatives. "I always thought my dad's life was so glamorous and that if I just lost 20 lbs., I could be a part of it," explains Alexis, who, after her parents split in 1986, was raised in Dallas by her mother, socialite Twinkle Underwood, 49. Following five months of outpatient treatment and continuing therapy with an eating-disorders specialist, Alexis, 26, is now healthy and a production executive in Los Angeles. She recently joined Bayou, 50, who lives in L.A. with his partner, agent Mark Itkin, and PEOPLE correspondent Vicki Sheff-Cahan, to discuss publicly for the first time her difficult journey back from her eating disorder—and how her father helped to save her life.

ALEXIS: When I went to college, everyone was blonde, big-breasted and thin. I wanted to look like that, so I started taking over-the-counter diet pills. Then I would throw up every time I felt too full. Everyone there was doing it—I can remember going back to the dorm after a meal and smelling vomit everywhere.

BAYOU: Everything changed when she went to college. Overnight it was, "I have to get into a sorority. I have to lose weight." It was almost an obsession. I didn't quite get it, but then I thought, "Every girl must go through this phase."

ALEXIS: I remember the first time I saw you on Christmas break my freshman year and you said I looked so beautiful. I said, "Well, I've been working out and eating right."

BAYOU: It was a dramatic change, but it seemed reasonable. Listen, I live in a world of fit, beautiful people—or I thought they were. But I've learned better: It's impossible to be that thin and be healthy. Nobody can live up to those images, and I think the fact that Alexis was around it all the time because of my work had to affect her.

ALEXIS: It did. I was always very embarrassed that I couldn't fit into any of the designer samples sent to my dad. I thought if only I could fit into the same clothes those models do, I would be beautiful; I saw myself much heavier than I really was. It wasn't until my sister Natalie [now 25 and a nurse] visited me that it came out that I had a problem. At the time, I was taking between 8 and 10 laxatives a day and throwing up. I was pretty thin; I'm 5'8" and weighed around 110 lbs. She immediately called my dad.

BAYOU: When I answered the phone, I heard Alexis crying hysterically in the background. Alexis never cries. While driving to her house, I remembered the time three years before when I had taken Alexis to the emergency room because of heart flutters. She was freaked out because she thought she was having a heart attack.

ALEXIS: They found that I had no potassium in my body. I told my dad I had tried a diet pill for the first time. But I knew it was from all the laxatives, diet pills and throwing up.

BAYOU: I told her it was stupid to take diet pills, but I didn't think anything of it. If she'd said, "I've just taken a bunch of crack," then I'd have been concerned. But when she called me crying, I suddenly realized it had been going on since then. I thought, "How stupid can I be? I had no idea."

ALEXIS: My dad kept saying, "I don't understand. You're a gorgeous girl." I tried to explain to him that it's a disease, a compulsion. When I went into therapy, I learned self-acceptance; when I was finally able to see myself as who I really was, I couldn't believe I had put myself and my body through so much torture. Today I eat when I'm hungry, and when I feel bad, I don't turn to food. If I'm thinking, "He doesn't like me because I'm not thin enough," or whatever is going on, I write about it. I talk about it. I'm honest about it. I'll call my dad.

BAYOU: That's something she would never do before. This experience has brought us closer. When something like this happens, it makes you realize that your kids are the most important things in life. I'd forgotten that.