Khulu Reinfirst Manyuka is thought to have left his home for the wilderness to pray, according to to Nehanda Radio.
The 73-year-old was known by the local community as "a very spiritual person whose faith could move mountains."
A relative said: "He was a very spiritual man. It's unfortunate he had to die this way."
Mr Manyuka is believed to have died after 30 days: "After a month we got the sad news of his death," the relative said.
Another family member added that he had no history of illness: "He was a healthy and religious old man who did not even look his age."
His body was found by a stranger who notified the police.
A local police spokesperson said he is not the first person to die from fasting, with "numerous" other cases reported: "We have received such reports before, but we cannot stop the public from fasting."
