[indubitable]

The problem with things like sedentary lifestyles is similar to the problem with internet correlations, which in either case imply the same thing. Compare the US to other nations experiencing similar problems and it's reasonably clear that whatever our issue is, it's unlikely because of lifestyle changes alone. Other similarly well developed nations with lackadaisical lifestyles don't suffer the same problems, yet impoverished nations such as those in the Pacific isles do. And in many cases, the problems are confined by our invisible borders. The Czech Republic is a good example there. Bordered by Poland, Germany, Austria, and Slovakia. Czechia is rapidly approaching problem levels, its neighbors are not.

There's a great distance between cholera and less filtered water. Worldwide the high end estimate of cholera deaths is 130,000 and that is with liberal modeling of unreported deaths. A quick search informs [1] that about 2 billion people a year rely on water that is absolutely contaminated with feces. That's a 0.0065% death rate at the high end. Usage of isolated or private water sources along with basic testing can trivially reduce these risks down to 0. And on that note of giving context to numbers, we should look at things like the opioid epidemic. In the US in 2015 about 15,000 people died from all opioids. Even if we assume that it was 0 before, which it was not, that would not explain the ongoing decline in life expectancy. The real reason is mortality rates from a wide array of diseases including 8 of the top 10 killers, heart disease in particular, continue to rapidly grow alongside our unhealthfulness. And that was after they had been in decline for decades.

[1] - https://www.compassion.com/poverty/water.htm