Charles Bronson, known as Britain's most violent inmate, has reportedly given up chocolate and been doing 2,000 press ups each day in his jail cell. He claims that he has managed to reduce his weight from 17 stone to 14 stone in nine months.
The 62-year-old inmate, who has written a letter about his new healthy lifestyle, notes that he used to gorge on a dozen chocolate bars each prison visitation day, amounting to 3,000 calories.
One meal a day
Bronson reportedly drinks up to eight pints of water a day and downs egg whites for breakfast - 18 of them each week. He also has the odd cup of tea without sugar, according to the Daily Mirror.
He said: "For the last 6 months I've only been eating one meal a day - apart from a bowl of soup at lunchtime. Bronson treats himself only to one slice of malt loaf cake - a sweet and chewy cake made from malt and raisins each day.
Aka Charles Salvador
Charles Bronson changed his name to Charles Salvador last year to honour of his favourite painter, Salvador Dali, "I really do feel great, fit, fast and healthy - I deliberately lost three-and-a-half stone - I'm now 14 stone - solid, no fat," he writes in a letter published on Facebook Page dedicated to his artwork.
The letter also offers advice from the prisoner, who urges his fans to get fit in the park instead of paying thousands of pounds for a gym membership.
The Luton-born bare-knuckle boxer and painter began life in prison with a seven-year sentence for armed robbery on a Post Office in Little Sutton in 1974, from which he stole £26.18.
Bronson earned the title of 'Britain's most violent inmate' for brawling and fighting with other inmates and prison guards during his time behind bars and vandalised buildings.
He has spent almost 40 years behind bars, was released in October 1988, but was arrested again after 68 days. He is due to be released for the first time in 25 years in 2016.
Charles Bronson's release
This week, former fiancée Lorraine Etherington revealed he is confident of his chances of release on parole next year. She insists he is now a changed man and deserves to be allowed to rejoin society. "For someone that hasn't murdered or raped, and poses no threat to the public - I find that extraordinary," she tells the Daily Star.
"He has a lot of supporting evidence to show his good work and willingness to want to progress." In 2008, actor Tom Hardy starred in his biopic, titled Bronson.