The total number of people with at least one chronic medical condition is pretty huge (possibly even a majority), which gets obscured because we usually only talk about prevalence for individual diseases/disorders.

That's a tad worrying. I've found some statements to that effect when I did a search on that last night and some stuff about obesity, do you have any sources giving a breakdown tied to individuals (not names, but like person#whatever has X Y Z) so I'm not double-counting?