From what I’ve read (multiple books written by defectors) and other resources, I really doubt the public “face” of this issue is that he is losing weight because he is sick/dieting/whatever. Instead, North Koreans are taught that he is large because he is a god.
In April Kim called on his officials to “wage another, more difficult ‘Arduous March’ in order to relieve the people of the difficulty, even a little”....the country faces again dire food shortages and economic instability...Kim has called the food situation “tense” on Jun 21, 2021
Perhaps his loss of weight might be purposeful for his own healths sake, but it would certainly put Kim in the position of identifying with the people that he too is going without...(though of course he's not).
His border with China is shut down because of covid....depriving the people of their black market incomes and food exchanges, plus the sanctions. Plus Hunger and malnourishment were reality there before covid or the sanctions so it won't take much for the Koreans to go headlong into famine itself..which they're already experiencing
I'm afraid Kim will let peple die in masses in order to get International attention and food supplied once again..ifhe follows his fathers pattern