Meet the American girl, 21, who has to eat every 15 mins to stay alive

An American girl, who suffers from a rare and undiagnosed syndrome that prevents her from putting on weight, has to eat every 15 minutes in order to stay alive.

Lizzie Velasquez, 21, from Austin, Texas, who is a communications student, weighs just four stone and has almost zero percent body fat, but she is not anorexic.

And despite eating up to 60 small meals, which consist of between 5,000 and 8,000 calories, daily, she still weighs just a little over 4st 3lbs.

"I weigh myself regularly and if I gain even one pound I get really excited," the Telegraph quoted Velasquez, who wears size triple zero clothes, as saying.

"I eat every 15-20 minutes to keep my energy levels up."

"I eat small portions of crisps, sweets, chocolate, pizza, chicken, cake, doughnuts, ice cream, noodles and pop tarts all day long, so I get pretty upset when people accuse me of being anorexic," she explained.

Velasquez had been born four weeks prematurely weighing just 2lb 10oz, and doctors had found that there was minimal amniotic fluid protecting her in the womb.

Her mother Rita, 45, a church secretary, who kept track of her daughter's health in dozens of notebooks, said doctors had given up on her surviving and did not expect her to.

Doctors speculated that she might have the genetic disorder De Barsy syndrome but soon ruled it out as it became clear she did not have learning difficulties.

Genetic experts they visited could not diagnose her illness, and her case fascinated doctors all over the world.

Now she is part of a genetic study run by Professor Abhimanyu Garg, MD, at the University of Texas Southwestern Medical Center in Dallas.

Professor Garg and his team now believe Velasquez may have a form of Neonatal Progeroid Syndrome (NPS) which causes accelerated ageing, fat loss from the face and body, and tissue degeneration.

People with PRS often have triangular and prematurely aged faces with a pointy nose.

"I am aware of a small number of people that have similar conditions to Lizzie but each case is slightly different," he said.

"We cannot predict what will happen to Lizzie in the future as the medical community are yet to document older people with NPS.

"However Lizzie is lucky to have healthy teeth, organs and bones so the outlook is good. We will continue to study her case and learn from her," he added.