Out of 166 detainees held at the prison on the US naval base in Guantanamo Bay, Cuba, 80 inmates are refusing to eat,spokesman Lieutenant Colonel Todd Breasseale told AFP.
They include 46 who are on a list for possible force feeding through nasal tubes while three are under observation at a hospital, he said.
The decline in hunger strikers -- which at one point rose to 106 detainees -- comes five months after the inmates launched their protest at the controversial War on Terror prison.
Although the US military has offered no definitive explanation as to why the number of strikers declined, the change coincided with the start of the Islamic holy month of Ramadan last week.
Also Read
Detainees who agree not to go on hunger strike are allowed to live in communal conditions and interact with other inmates, allowing the detainees to participate in Ramadan prayers,officials said.
A large number of detainees were transferred to solitary cells in April after an incident that US authorities called a revolt.
US judge Rosemary Collyer ruled she did not have jurisdiction in the case because Congress has adopted laws that place the Guantanamo detainees outside the authority of the federal courts.
And she concluded there was nothing "so shocking or inhumane in the treatment" of the inmates that indicated a possible violation of the US Constitution.
She said the inmates did not have the right to starve to death and that the government had a legal duty to prevent suicide and starvation.