At the age of seven, the boy weighed almost 50 kilograms and had a body mass index roughly double what it should have been.

Despite hospital staff giving his parents a weight-management plan, the child put on another six kilograms in the six weeks after he left John Hunter Children's Hospital in Newcastle. Two years later, aged 10, he was dead due to complications from obesity.

Newcastle Coroner's Court is examining the boy's death, including any role played by his parents, the Department of Family and Community Services and the NSW Department of Education and Training.

The boy was rushed to hospital on September 17, 2010 and died 12 days later. He had suffered a massive brain injury from lack of oxygen, which was related to his morbid obesity, counsel assisting the inquest Ian Bourke said.

The child, who cannot be identified, had a lengthy history of health problems, the inquest heard.