Forty-six detainees joined 38 already on strike on Dec. 25, said Guantanamo spokesman Lt. Col. Jeremy Martin, who added that the number of fasting detainees "routinely fluctuates."
"On the anniversary of Sept. 11, the number of strikers spiked to 131," Martin said. "They steadily decreased over the weeks and months until Dec. 25, and then they spiked again."
Thirty-two fasting detainees were being fed through tubes, either through their noses or intravenously.
Hunger strikers have allege inhumane and cruel treatment, charges the U.S. has repeatedly denied.
The military classifies detainees who miss nine straight meals as being on a hunger strike. The current fast began Aug. 8.
Many of the detainees at Guantanamo have been held more than 3 1/2 years without charge or access to lawyers. Most were captured in Afghanistan and are suspected of ties to Al Qaeda or the ousted Taliban regime that sheltered the terrorist network.
At Guantanamo Bay, the U.S. military holds about 500 detainees suspected of terrorist activities.
The prison has become the focus of criticism of America overseas and at home. Initially, the Bush administration refused to let the men see attorneys or challenge their imprisonment in courts. The Supreme Court in 2004 said U.S. courts were open to filings from the men, although justices may be called on to clarify the legal rights of the detainees in a separate appeal.
Defense Secretary Donald H. Rumsfeld has said he believes some Guantanamo detainees have been conducting hunger strikes to capture press attention.