Henry Ranson Lloyd, 17, died of natural causes on 21 January 2014. Police said his Conwy home was litter-strewn.
Calls to make it easier for councils to monitor the quality of home schooling and pupils' welfare were made at the inquest in Ruthin, Denbighshire.
Coroner John Gittins said it was "staggering" people were home educated without councils "having any teeth".
Henry died at his home after complaining he could not breathe properly.
Emergency services were called but he could not be saved.
Pathologist Dr Andrew Dalton said the 6ft 2in teenager was "markedly obese" and had a blood clot.
Conwy council's head of education Richard Ellis Owen told the inquest several attempts were made to engage with the family, but there was no response.
"If parents wish not to engage with us there's hardly anything we can do," he said.
But Henry's mother Jennie Ranson told the inquest she did not feel she had let him down, saying "he knew he was loved".
Mr Owen said it was possible children could slip through the net and asked the coroner to write to the Welsh government "expressing the difficulties we have in terms of monitoring the quality of education and welfare of people".
"If we haven't any legal backing to that we are in a difficult position," he added.
Mr Gittins recorded a conclusion of death due to natural causes and said the involvement of social services, environmental health and other agencies was "limited."
He said: "I take on board what I was told by Richard Ellis Owen which concerns the question of home education.
"It seems staggering to me that people can be in a home situation without the local authority having real teeth with regard to checking up on progress and keeping an eye on them generally."
A home-schooled 19-stone teenager died from deep vein thrombosis, an inquest has heard.