His defiance has turned him into a hero of Iran's opposition movement, and Khazali vowed to continue his strike until he is released.
The opposition "Kalame" website reports that Khazali has now escalated his protest by going on a "dry hunger strike," meaning that he is also refusing to drink liquids, on which he had been surviving since he stopped eating.
Khazali, the son of prominent hard-line cleric Ayatollah Khazali, was arrested on January 9 and later sentenced to 14 years in prison.
Khazali's father has publicly distanced himself from him and accused his son of deviating from the right path.
The outspoken blogger and ophthalmologist has been in and out of jail over the past three years over his criticism of the Iranian establishment. Before his arrest, Khazali had called for a boycott of last week's parliamentary elections.
Last month, he issued a letter from jail in which he describes some of the difficult conditions under which Iranian prisoners live and the unfair trials some have been facing. He says several of his co-detainees have been sentenced to 17 years in prison following trials that lasted "2 minutes" and without any solid evidence being presented:
Khazali's son said in late February that his father had been transferred to a hospital after his health deteriorated.
"When we saw him in the hospital, we couldn't believe it was him," Khazali's son told the International Campaign for Human Rights in Iran on Feb 24. "His weight loss was unbelievable; he was so thin. We are afraid something bad might happen to my father."
Hunger striking has become one of the only remaining forms of protest for political prisoners in Iran, who are often said to be put on trial without access to a legal representation.
Last week, former hard-line columnist and documentary filmmaker Mohammad Nourizad called on Khazali to end his hunger strike. Nourizad, who had also gone on hunger strike while in jail to protest his conditions, told RFE/RL he issued his open letter following a request by Khazali's 16-year-old son, who is extremely worried about his father.
Nourizad, however, said he doesn't think such letters will have any impact on Khazali's resolve.
"Individuals who are in such situations [in jail] don't pay attention to these things. I remember when I was on hunger strike in jail, some prisoners walked by my cell and one of them shouted that some political figure wanted me to stop my strike. But at that moment, it was as if I hadn't heard him," Nourizad said, adding that he believes Khazali is in the same situation.
Nourizad is widely admired among opposition members over his criticism of the postelection crackdown and human rights abuses in Iran.
In past months, Nourizad has challenged Iran's supreme leader in more than 25 letters he has released on his website and social media sites.