"The trial of Seselj is suspended until such time as he is fit enough to fully participate in the proceedings as a self-represented accused," the ICTY said.
The Serbian nationalist insisted on representing himself at the court, as did the late Serbian leader Slobodan Milosevic.
In addition to appealing the decision to appoint a lawyer against his will, Seselj demanded the removal of the tribunal's three judges whom he accuses of bias.
Seselj faces charges of having formed a joint criminal enterprise together with Milosevic in 1991-1993 aimed at driving non-Serbs from parts of Croatia, Bosnia and northern Serbia to create an "ethnically pure" Greater Serbia.
During his hunger strike, Seselj only accepted water and refused food as well as medicine for a number of health complications.
The UN tribunal said that it had ordered him to be force-fed if necessary after doctors who examined him said he could die from a heart attack within days, or starvation within two weeks.