The documentary's voice-over, according to Reuters, said: "The wealth and prosperity of our socialism is thanks to the painstaking efforts of our marshal, who keeps lighting the path for the people, like the flicker of a flame, despite suffering discomfort."
In July, North Korean state television showed a video of Kim appearing to limp during a ceremony to commemorate the 20th anniversary of the death of his grandfather, former North Korean leader Kim Il Sung. The unusual footage prompted many to speculate about Kim's health.
That speculation only increased in recent days; although Kim is usually a fixture of North Korean state media, his most recent public appearance was on Sept. 3, when he attended a concert with his wife.
Although the report did not elaborate on the nature of Kim's "discomfort," South Korean media and other North Korea watchers are full of ideas of what might be wrong with the dictator.
South Korea's Yonhap news agency, for instance, reported that the North Korean leader could be suffering from gout, based on the limp, citing an unnamed source and the history of gout in Kim's family.
Gout is often associated with rich diets, but genetics also contribute to the development of the disease.
A South Korean official told The Wall Street Journal that the South Korean government also believes Kim has gout, along with several other health issues, including "diabetes, high blood pressure and obesity."
As Adam Taylor wrote on Thursday, there also has been speculation that security concerns may have been a factor in Kim's disappearance from public view.
"Another reason why Kim may be reluctant to appear in public is the ongoing power struggle inside the North Korean military, which means that the situation in Pyongyang is still unstable," Toshimitsu Shigemura, a professor at Tokyo's Waseda University, told the Daily Telegraph. Late last year, Kim had his own uncle executed, which many observers took as a sign of a surprising and unusual power struggle in Pyongyang.
According to NK News, Kim was absent for two weeks in 2012 and later returned to the public eye with no explanation.