Van Nath is one of only three people still alive who experienced Tuol Sleng
One of the few survivors of the Khmer Rouge regime's notorious Tuol Sleng detention centre has testified at a UN-backed tribunal in Cambodia.
Van Nath described how hunger had driven him to eat insects, and said he had also eaten the food beside corpses of starved fellow prisoners.
He was appearing at the trial of the man who ran the prison, Comrade Duch.
About 15,000 people were detained at Tuol Sleng in the late 1970s, but only seven are thought to have survived.
Van Nath has been waiting for his day in court for 30 years.
The tribunal has already heard plenty from Comrade Duch himself - as well as a number of expert witnesses.
WHO WERE THE KHMER ROUGE?
Maoist regime that ruled Cambodia from 1975-1979
Founded and led by Pol Pot, who died in 1998
Abolished religion, schools and currency in a bid to create agrarian utopia
Up to two million people thought to have died from starvation, overwork or execution
But according to the BBC's Guy DeLauney in Phnom Penh, Van Nath can provide a unique perspective, as one of only three men still alive who know what it is like to have been a prisoner at Tuol Sleng.
"The conditions were so inhumane and the food was so little," Van Nath told the tribunal, as he broke down in tears. "I even thought eating human flesh would be a good meal."
He said he was fed twice a day, but each meal only consisted of three teaspoons of rice porridge.
"We were so hungry, we would eat insects that dropped from the ceiling," he said. "We ate our meals next to dead bodies, and we didn't care because we were like animals."
He described how prisoners were kept shackled - 20 or 30 of them together - and ordered not to speak or move.
Van Nath owed his survival to his skills as a painter. He was forced to produce portraits of Khmer Rouge leaders - on pain of death.
"I thought that if I could do good pictures and they were satisfied with what I painted, they would be happy and I would survive," said Van Nath before taking the stand.
Van Nath's portraits passed muster - and he has since become one of Cambodia's most famous artists, and his work often depicts scenes from Tuol Sleng.
Admission of guilt
Comrade Duch, whose real name is Kaing Guek Eav, is accused of overseeing the torture and extermination of prisoners at the jail.
Earlier in his trial, the 66-year-old admitted responsibility for his role as governor of the jail, and begged forgiveness from his victims.
But he also insisted that he did not hold a senior role in the regime, and that he had had little choice but to work there.
Four other former Khmer Rouge leaders are currently in detention at the court, and are expected to face trial in 2010.