Paul Ward (33), the man convicted of murdering the journalist Veronica Guerin, has lost more than a stone in weight after refusing to eat prison meals almost since his court case at the end of November.
Prison sources said Ward has been living on a diet of chocolate bars and soft drinks since mid-December in Portlaoise but has not been on hunger-strike and has not made any specific protest to the authorities.
There was speculation that the authorities might have to move Ward to the secure wing of the county hospital, but he has indicated that he does not want to leave the prison.
He has been examined by doctors and a psychiatrist and is not said to be ill or mentally unwell. Ward, a former drug addict, is said to have lived on chocolate bars and soft drinks for long periods when he was taking heroin.
However, it is understood he has felt under pressure from other inmates and from prison staff since his conviction for murdering Ms Guerin in June 1996.
Former criminal associates of Ward's in Portlaoise are said to have shunned him since his decision to give evidence in his trial about his drug-dealing activities.
Ward is also treated as a high security risk by the prison authorities since he was involved in the taking of two prison officers hostage during a four-day siege in Mountjoy Prison in January 1997, when he was on remand awaiting trial for the murder.