[3] Renn started her modeling career in high fashion at the age of 14 after being spotted by a professional scout in her hometown in Clinton, Mississippi.

Renn has authored a book, Hungry: A Young Model's Story of Appetite, Ambition and the Ultimate Embrace of Curves,[5] about her experiences in the fashion industry in relation to her several body type transformations.

On June 30, 2007, Renn married her longtime boyfriend Gregory Vrecenak at the Church of St. Ignatius Loyola in Manhattan, New York.

[8] She has walked the runways for Shiatzy Chen, Chanel, Zac Posen, Vena Cava, Heatherette, Elena Miro, and Jean Paul Gaultier.

Renan has appeared in campaigns for Philipp Plein, Chanel, Dolce & Gabbana, Jean Paul Gaultier, Jimmy Choo, DSquared², Zac Posen, Mango, Liz Claiborne, Barneys New York, Saks Fifth Avenue, Lord & Taylor, Nordstrom, and H&M.