Sure. Now compare their amounts of muscular mass, and the percentages of body fat. I think the real problem is doing the same thing many hours a day, every day

Sure. Now compare their amounts of muscular mass, and the percentages of body fat. I think the real problem is doing the same thing many hours a day, every day, all year long, for decades. Whether that's sitting, or felling trees, it appears to be equally bad, just in different ways. We are shaped by evolution for a more varied lifestyle.