Photos: Meet The World's Thinnest Girl

At just 5ft 2" tall and weighing in at 4st 3lb, Lizzie Velasquez, 24, appears worryingly thin at first glance. But her tiny frame wasn't caused by an eating disorder. Instead, it is the result of a syndrome so rare that it is shared by just two other people. Her condition means that try as she might, Lizzie, from Austin in Texas, finds it impossible to gain weight or store fat, and as a result, she's forced to eat up to 60 small meals a day. Continue to see more pictures and read more about her after the cut....

Despite the challenges, the courageous 24-year-old insists she wouldn't change a thing about herself and, instead, throws herself into her work as a motivational speaker and anti-bullying campaigner. Speaking in TLC documentary, Body Bizarre, Lizzie, who was tormented by school bullies and has endured vile abuse online, said she has no intention of attempting to 'fit in'.

Although the precise nature of Lizzie's condition remains shrouded in mystery, what is clear is that she was born without adipose tissue - body fat. The main symptom of the condition is an inability to gain weight, although it also appears to affect vision. The 24-year-old's condition is particularly puzzling because it takes on aspects of other syndromes, including progeria. Progeria, which is a form of accelerated ageing, has physical symptoms shared by Lizzie including a pointed nose, small mouth and ageing skin.