A 23-stone cannibal, who is serving a 21-year manslaughter sentence in a British prison, has received gastric band surgery in a private hospital that cost the National Health Service (NHS) £15,000.

The Sun reported that 39-year-old Graham Fisher received the weight-loss surgery after he became shockingly obese on a diet of chips, chocolates and cake, the Sun reports.

A spokesperson for the NHS defended the decision to spend the taxpayers’ money on Fisher's surgery.

Defending Fisher's right to the surgery, the spokesperson said, “People receiving treatment for mental illness are entitled to the same level of care as anyone else.”

Fisher was found guilty of cannibalism. In late 1990s, he strangled and burned two of his neighbors and ate the flesh from their bodies. Some days later, he attempted to kill a 19-year-old Czech student on a running train.

Fisher confessed to the crimes to his psychiatric consultant in 2010 during a separate prison sentence for sexually assaulting two Spanish students.