I don't know how obvious that is a priori. If you asked a subsistence laborer what the effects of sitting all day would have on their health you might get a different answer.
Indeed, doing physical labor all day is also quite terrible for you. My godfather was a farmer in rural Mexico and by his 50s his body was in pretty bad shape.
And that's why your pension was set at 60 or 65, and why developed countries are having a hard time paying for them. In the past physical work meant that by the time people were old enough to collect their pension they were worn out.
Attempting to quantify the obvious is noble work. Haven't you seen how popular those sorts of articles are around here.
I only use the word obvious for sarcasm. Nothing is obvious without domain knowledge.