At the age of seven, the boy weighed almost 50kg 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 6kg in the six weeks after he left John Hunter Children's Hospital in Newcastle, Australia. 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.

His health and his parents' drug use made him the subject of four ''risk of harm'' reviews by Family and Community Services between 2008 and 2010, but the department closed those reviews to pursue the needs of other children deemed to be at greater risk of harm, Mr Bourke said.

The boy had sleep apnoea, related to his obesity, and by mid-2009 he weighed almost 70kg. Medical appointments were made for him, including with a surgeon to decide if he should have his tonsils and adenoids removed, but many appointments were missed and the surgery never took place, the court heard. He had already missed 103 days of school in the year he died.

Police investigated the death yet the circumstances leading to the boy's admission to hospital in September 2010 were unclear, Mr Bourke said. It appeared he was found slumped on a lounge and stopped breathing on the way to hospital. Doctors were able to revive him and put him on life support, but after 12 minutes or more without oxygen he had suffered a massive brain injury, Mr Bourke said.

The inquest continues.