He does not do anything for his health obviously. He is fat and does not exercise. Of course he gets the best possible care when he is ill. But what happens if he dies in the near future? His son is a toddler.
Will his sister take over? But is North Korea ready for a female leader?
We are famous for "Stockholm syndrome": "Q: Hey, what's up with Matt? His Dad is on social security, his mom got laid off, his sister's kids get free school lunches, he collects federal financial aid for college, and he only makes minimum wage working at Walmarts. Yet he keeps talking about how we need to cut taxes for the wealthy and quit spending so much on social programs. A: Yeah, he thinks he's going to be a millionaire soon. He's got Economic Stockholm Syndrome." (Urban Dictionary)
Kim Jong-un's younger sister, Kim Yo-jong is best placed to take over as supreme leader if he were to die, or would be if she were male. Interestingly, it is rumoured that she married in January 2015 when she was five months pregnant, not to the father of her child who was a palace guard but to an old school friend with an official position in either the military or the government. I love rumours.