Bentley-driving Stephen Sussams, 59, who swindled nearly £15,000 in housing and council tax benefit, appeared at Croydon Magistrates' Court, where his lawyer claimed he should not be jailed because he is obese.
But Judge Peter Gower ignored the plea and ordered Sussams, who also stole £17,000 from a dead man's bank account, be jailed.
Sussams, from Norbury, denied four counts of benefit fraud and one count of theft, but was found guilty after a trial.
Matthew Groves, representing the swindler, told the court a custodial sentence "would be a great burden for him to carry because of his ill health", which includes "diabetes, heart disease, hypertension, obesity and depression".
"Given his ill health and positive aspects of his character, action doesn't [need to] involve a third period of custody," Mr Groves added, referring to his client's convictions for producing cannabis in 1996 and for possession of the drug in the 1980s.
Sussams, who owned The Royal Dart in Dartmouth – which boasted a champagne-marinated burger meal with black truffle costing £125 – began scamming £17,600 from the account of an elderly man he used to care for the day after he died.
He withdrew funds from Keith Dickenson's account in five instalments following his death in 2008, before taking over the tenancy of his house which he fraudulently claimed housing and council tax benefit for until September 2011.
Carers' supplements continued to be paid into Mr Dickenson's account, for which Sussams was a signatory, after he died because the benefit cheat did not inform the authorities he had died.
As Sussams continued to withdraw funds from the dead man's account, Croydon Council grew suspicious and investigated.
Sentencing Sussams to eight months' imprisonment for the count of theft, Judge Gower said:
It is clear from the outset that you knew full well that that was money that the council had mistakenly paid into the account of Keith Dickenson after he died. I have no doubt that you knew that money was intended by the council to cover the cost of providing care services to him appropriate to the level of his disability and knew it was no longer needed for that purpose. Instead of returning these you applied them in accordance with your own wishes.Sentencing him to a further four months for the counts of benefit fraud, he added: "Your claim for these benefits was fraudulent from the outset."