Oh yeah because it's so taxing to sit in the air conditioned cab of plant machinery and push levers all day. Come on, you really think modern construction actually required any kind of physical exertion? This isn't the 1930's. That's why builders are always f*cking fat. I probably exert more energy sat at my desk.
Really, i generally do not go into this kind of threads because of my ignorance on such subjects, and i neither like to go off topic much, but wow, to consider being a builder an easy job that does not require a really healthy physique ever is quite ignorant.
Sure size of constructions does not say a lot about how much energy from the workers it costed to build said construction, but i sure can say that building crap for people can be exhausting as f*ck.
Worst are medium to heavy renovations at hard to reach areas, but just breaking off your standard brick wall with a concrete breaker for a whole day even at the most ideal of conditions is gonna put physical pressure on a person.
Same for bringing in 25 kg bags of concrete, carrying ruble out of houses, any work that revolves around going up and down stairs a lot, ect...
If you see a builder being really overweight, it is either because that kind of builder is specializing into something like being a plummer, controlling cranes, flushing walls, and other things like that.
Or...and this is also pretty common, they are the kind of idiot that is first gonna nearly starve themselves to death during the day, delaying the moment to take in a proper meal, or just skipping a proper meal entirely, or/and then is stuffing themselves full at the end of the day with anything they can eat.
Last thing is very common among the ones that lead the teams and such so far i have seen.
Also none of that hard work is gonna do what some kind of workout is gonna do, except for giving you more muscular arms, giving you more stamina and making you tired at the end when all is done for the day.
But yea, any limbs, the back, hand and feet are at risk of being forced by to much strain being put on them.
And again, this all depends on the work given.
Not gonna lie, in the 3 years i worked at such a place i also got plenty of days were all i was doing was filling up holes with concrete, flushing small gaps and just cleaning tiles...but yea, do even that kind of sh*t for a few days and even with some soft protection under your knees you will be feeling what you have done, even though there will no evidence of it except for a few stains on your trousers.
Really, i got no sources on those things except my own experience, you got to trust me on this one