Talk of the reclusive North Korean leader's health emerged anew this week when he made a rare public appearance Tuesday in a surprise meeting with Chinese Foreign Minister Yang Jiechi in Pyongyang. Chinese television footage showed Kim shaking hands with the guest and brandishing a big smile.
That image was the first publicly available video of the secretive Kim since late April when he reviewed a massive military parade from a balcony over Pyongyang's main plaza, clapping and waving to his troops as they hysterically shouted cheers, appearing deeply moved by a rare glimpse of Kim.
The 65-year-old leader - revered as a near-demigod in the totalitarian nation - looked generally well in the latest footage. But compared with the April clip, he appeared a bit thinner and had less hair. Some South Korean media made similar observations, and engaged in renewed speculation about his health.
Kim's latest public appearance came after unconfirmed news reports that he had undergone some kind of heart procedure in May, supposedly performed by German doctors flown to Pyongyang, and was so weak he could not walk more than 30 meters (yards) without resting.
In response to queries last month, the German Heart Institute Berlin said it had dispatched a team of doctors to North Korea to perform operations there - but not on Kim Jong Il.
Still, South Korea's Dong-a Ilbo, one of the country's three largest mass-circulation newspapers, speculated this week that the reported heart surgery might have made Kim "markedly leaner" and caused him to lose some hair. Such symptoms are common in patients who have undergone heart surgery, it said.
Kim Won-jang, a cardiologist at Seoul's Asan Medical Center, said some patients can lose appetite and thus weight after a heart operation, but not all do.
Nobody but North Korea can give a definite answer about Kim's health conditions. But the regime - which is one of the world's most closed, and which tolerates no independent press - has never made any comment on the issue of Kim's health, an absolute taboo in the communist country.
South Korea's main spy agency, the National Intelligence Service, said last month that Kim has long had heart disease and diabetes, but that there has been no sign that the chronic ailments have progressed enough to affect his public activity.
"Our assessment of his health remains unchanged," an NIS official said Friday on condition of anonymity, citing office guidelines. The official also said the agency does not believe the report that Kim had a heart procedure. He declined to elaborate.
Some analysts agree that Kim's health conditions are nowhere near being serious.
"We can't assess his health conditions just by pictures, but even by the pictures, he didn't look that different from before," said Koh Yu-hwan, a renowned North Korea expert at Seoul's Dongguk University. "I think there is no possibility of a mishap, at least in the next one year or two," he said of the possibility of Kim falling critically sick and dying.
Paik Hak-soon, another top North Korea expert at the Sejong Institute outside Seoul, said that Kim looked a bit thinner and had less hair than before, but added that he believes Kim's health conditions are not serious enough to affect his ability to rule the nation.
"How old is he? Anybody of that age has some adult diseases," he said.
Kim's health has been a focus of international attention because his fate is believed to be tied to that of the isolated, nuclear-armed nation he leads. Kim has ruled the North with an iron fist since the death of his father, who established a personality cult that has survived his passing.
The younger Kim, said to have a fondness for fine food, expensive alcoholic drinks like cognac and a passion for Western movies, has three known sons, but has not yet publicly designated any as his successor.
His health is of particular concern now as international efforts spearheaded by China, Japan, Russia, South Korea and the United States - along with Pyongyang as part of the six-party forum set up to rid the country of nuclear weapons - gain momentum.
North Korea, which alarmed the world by conducting its first atomic test explosion last October, pledged in February to shut down its plutonium-producing nuclear reactor in exchange for economic and political concessions.
After months of delay, Kim's regime appears to be moving to fulfill that pledge, reaching an agreement last week with the U.N. nuclear watchdog over how to verify and monitor the planned shutdown.
"Even a person who has long been healthy can become ill or exhausted if they reach that age," said Kim Keun-sik, a North Korea expert at South Korea's Kyungnam University. "I think Kim Jong Il may have become thinner these days because of stress" over the nuclear issue, he said.