It's really not the governments job to regulate weight, unless you are a die hard statist. This is pretty distinguished mentally-challenged.
It is the government's job to look after its citizens' health. Being obese leads to numerous risk factors which of course are health-related.
I can definitely see their train of logic here.
Then weigh them when they go for driver's licenses, don't impose penalties on their employers. What the fuck are companies gonna do if their employees don't wanna go on a diet? Fire them? How does that help society?
As if the government should be this involved in your shit anyway, and as if the single measurement of waistline means jack shit.
I agree the employers aren't the ones to blame. I also agree that it's ridiculous to use a waistband to measure. You'd need a proper weight assessment. And yes, get them when they apply for their ID card or drivers license.
But I think that while the execution would be flawed, the economic and social principles are sound. For the Japanese government they don't have the moral option of saying "screw you guys, we ain't footin' your medical bills anymore on account of you eating yourself to death". They have the "social obligation" to provide such services because they have done so for years and their tremendous sense of family and respect for elders ethically binds them to this "obligation".
This isn't the US we're talking about. The health system there isn't anything like the one in Japan, or Hong Kong, or Taiwan for that matter, where public healthcare infrastructure is frequently better than the private sector. That's got to have a pretty penny.