Do you not see the chicken-or-egg situation here? They're more unhealthy because of bad healthcare. That (bad) healthcare is more expensive because they're more unhealthy.

Moreover, much of the reason the healthcare is so expensive is because of insurance overhead, for-profit middlemen (including hospitals, private equity owning doctors offices, etc), massive prescription medication markups because people can't go without medication, and other inefficiencies in the system. Even with an unhealthy population, it doesn't need to be nearly as expensive as it is.