As an armchair economist, this is my personal favorite theory. With one of the most obese populations in the world, I think it's obvious that we'll also be the most sick and we'll have to spend a lot to try to dig ourselves out.
https://costplusdrugs.com/medications/albuterol-90mcg-inhale...
Obesity obviously doesn't cause high drug costs but it is a risk factor for asthma. Non-obese people are less likely to have to spend anything on inhalers.