The former TOWIE star is a known fitness fanatic with a hugely successful online fitness website but in a new interview she confesses she took it too far with dieting and exercise in the past.
Lucy told Fabulous magazine her stylish was forced to intervene during a photoshoot when Lucy's size six trousers were too large for her tiny frame.
"She told me I was too thin and said I needed to put on a bit of weight. Until then, I think people were a bit scared of saying anything to me," said Lucy.
"But I can see now how girls can get eating disorders, because being thin made me feel good. I don't think at the time I realised how thin I was."
Lucy was 8st 2lb at her lightest and says she was "addicted" to exercise because it made her feel good, not because she wanted to lose weight.
After her stylist intervened, she says she made a "conscious effort" to increase her calorie intake and restrict her workouts, and she's kept that up until now.
"I am not obsessive any more," she says. "I work out to stay fit and lean, not to lose weight."
As well as owning the successful Results With Lucy website, the ex-TOWIE star, 23, has just launched a book called Be Body Beautiful, which contains diet and exercise plans, as well as Lucy's own journey to achieving a fit and healthy body.
"I'm probably the happiest and most content I've ever been, but I've had to work really hard on my body and on my confidence to get here. This book is my personal journey, but it's also a diet and lifestyle plan that will help you transform your body and live a long, strong, healthy and happy life."
Reveal is now on Google Plus! Join us here for the latest pictures, fashion and celebrity news!