I happened to see a chart showing that among wealthy countries, the US is at the top for obesity and Japan is at the bottom. Just a correlated random fact that nobody knows the cause of either. Maybe something about fish consumption?
There are huge numbers of significant demographic differences between Japan and the US.
It's true that obesity is a factor in COVID death dates (as it is for most things) but there are plenty of places with lower levels of obesity with significantly higher death rates. Singapore and South Korea are better comparisons here and the death rate is significantly higher.
As for fish consumption - it's difficult to think of a reason why that would be significant for a respiritory disease like COVID. It wasn't for SARS.
