An Australian prisoner underwent a crash diet and successfully wiggled himself out of jail. He was nabbed again three days later.

Robert Cole, 37, did not eat and consumed laxatives to shed around 30 pounds. He was able to squeeze through a hole that he fashioned with a butter knife and flee from a hospital in a Sydney maximum security prison.

At 123 pounds, Cole made his way out through a hole between brickwork and a window frame, climbed a razor-wire fence, walked along a prison wall and then leaped to the outside.

Cole's lawyer Richard Leary told the New South Wales District Court that his mentally ill client had acted naively after failing to convince authorities he was fit for release, Australian Associated Press reported.

"He committed this offense in a vain hope to show authorities that he can survive outside," Leary said.

Judge Roger Dive said Cole's violation was serious and sentenced him to 21 months.

Dive said, "It has involved some time-consuming efforts and planning and preparation."

Cole was previously jailed on theft and assault charges. His sister Denise Roberts, said he had been suffering from a drug-induced psychosis for a long time.