Woman, 24, weighs 4st 3lb and has to eat every 20 minutes because of rare medical condition Lizzie, 24, from Texas, has a rare condition shared by just two other people She was born without body fat and finds it impossible to gain weight Bullied at school and online, she is now a motivational speaker and author Thanks to her experience, her ambition is to set up an anti-bullying charity 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. Inspiring: Lizzie, who suffers from a rare genetic disorder, is now a best-selling author of two books Slender: 4st 3lb Lizzie is unable to make or store body fat and has to eat every 20 minutes 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'. 'I would never, ever change my appearance, even if I could,' she explains. 'It's taken me so many years to accept who I am and like the person that I see in the mirror so I would never change it just to "fit in."' But despite her bravery, the condition, which is yet to be fully diagnosed and named, casts a shadow over her life, not least because most of the people who suffer from the syndrome die in childhood. Her doctor, Dr Abhimanyu Garg, says: 'Lizzie is one of the very few people in the world to have this condition. Family: Lizzie with her supportive parents, Lupe and Rita, and protective younger siblings, Marina and Chris Brave: Lizzie has had the condition all her life and tipped the scales at just 2lb 11oz when she was born 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. [Sufferers] have very little muscle mass, their limbs look very thin, spindly, and many of these people, they die very early in life. Other children with this have had very different experiences. Lizzie is 24 right now so she has beaten these odds. Thanks to the illness, Lizzie, who weighed just 2lb 11oz when she was born, has already lost the sight in her right eye and has limited use of the other. Nevertheless, she has refused to allow that to stop her and has penned two best-selling books, and works as a motivational speaker doing up to 200 talks a year. Many of her talks focus on a topic close to her heart: that of bullying. Seen speaking at her old school in a scene from the documentary, Lizzie reveals how becoming the subject of cruel comments, both at school and online, affected her life. My parents raised me to be completely normal. They never told me I was different,' she explains. The only thing is that I was smaller than the other kids but I was just like them. As I got older, I became more aware of why people were staring at me and I started getting really angry. I hated the fact that none of these kids wanted to get to know me. In my mind, I'm just like them and I would never tell my parents I was being bullied so my way of coping with it is when I would take a bath and nobody was in the room with me, and that's when I would cry.' But although dealing with school bullies was tough, a bigger test was to come after she was interviewed about her condition on national TV. Motivational: Lizzie now tours the USA giving up to 200 talks on the theme of bullying and how to tackle it Popular: Her motivational books, including Be Beautiful, Be You, are both best-sellers 'I was at home, online, and I saw a picture that was really familiar,' she reveals, gesturing towards a still from the interview that had been given the caption 'The Most Ugly Woman In The World', I felt like somebody was putting their hand through the computer screen and punching me over and over. There were thousands and thousands of comments. The first one said: "I just threw up over my keyboard. You're gross. The second, "eww, kill it with fire, now." Others asked why my parents didn't abort me because I'm so ugly. Can you imagine that? Despite the vile comments, Lizzie says she has no fear of bullies anymore and if she were to meet one in future, her response would be: 'I won'. For now, she's concentrating on the future and the anti-bullying charity she hopes to set up. 'My dreams for the future are continuing to help others,' she explains. I want to create an anti-bulling company. Something for kids and adults and teenagers who are struggling and so far, my dreams have come true. World's Thinnest Woman: Body Bizarre is on TLC UK at 10pm on Monday November 11