Gabby Williams, 8, weighs 5kg, has rare slow-ageing condition Eight year old Gabby Williams is one of just a handful of people in the world with a rare condition that slows the ageing process. Courtesy TLC/ABC News SHE'S eight years old and weighs just five kilograms. Gabby Williams feels like a newborn child and her mother has to care for her like one. Could this curious case of ageing hold the key to "biological immortality"? Gabby is from Billings, Montana in the United States and is one of just a handful of people in the world with a rare condition that slows the ageing process, ABC News reports. Medical researcher Richard F Walker has been studying Gabby for two years. His particular interest is investigating the cause of slow ageing. "In some people, something happens to them and the development process is retarded," he said. The rate of change in the body slows and is negligible. Gabby Williams is eight years old and weighs 5kg. In an ABC News special to be aired in the US this week, Gabby appears with two others who share her condition: a 29-year-old American with the body of a 10-year-old, and a 31-year-old Brazilian woman who's no bigger than a two-year-old girl. Gabby's mother cares for her daughter like a newborn child. Picture: ABC News Source: Supplied Dr Walker suspects that Gabby and the others may have a genetic impairment that interferes with a crucial process called "developmental inertia" that affects growth in humans. "Without that process we never develop," he said. When we develop, all the pieces of our body come together and change and are coordinated. Otherwise, there would be chaos. But Dr Walker's interest goes beyond curiosity. He suspects that through genetic mutation you could slow the ageing process and unlock "biological immortality." If we could identify the gene and then at young adulthood we could silence the expression of developmental inertia, find an off-switch, when you do that, there is perfect homeostasis and you are biologically immortal. Should we further explore a way to slow ageing, or are we trying to play god?