It hasn't.

> A majority of infrastructure in the US makes it extremely hard to be healthy

This is a copout.The only hard thing about being healthy is having the discipline to do so. Certainly more than 6.8% of people have the means to have healthy diet and they choose not to. There are definitely extreme cases of poverty where it would be difficult (which people who are well above that will use as an example to make themselves feel better about their choices) but I'd argue it's still very reasonable to be able to lead a very healthy lifestyle.

We're fat as hell because we live a life of extreme abundance.