I'll say one thing about construction laborers. They are in general in good shape. Just think about their work life style. They are on their feet for 10 to 14 hours. Constantly bending and picking up stuff. Carrying things. Digging ditches. Walking the site. Tough guys in general.
Now lets look at the typical getbigger. Drives to work and once there sits on his ass. When not working he is sitting watching tv/computer or playing video games. He drives every where. Hardly walks at all. His only cardio is walking on a treadmill at a pace he doesn't realize is slower that what normal people walk down the street. He works out in the gym for an hour 4 times a week but his life is so non moving that even this can't make up for his modern non moving life of rest. Don't tell me intensity is enough to make the difference. That's why perma bulkers have become such a big percentage of guys into bodybuilding. They are just fat out of shape guys carrying some muscle underneath.
These construction guys will regret their career choice once they hit 40+.
You can be perfectly healthy having a non physical sedentary job.
...and let me add, just because you work a physical job, does not mean you are healthy. Plenty smoke, stuff their face, do rec. drugs, and alcohol, not to mention the stress of having deadlines and pushing yourself physically on a regular basis can fuck with your health all on its own.
My neighbour was a healthy fella, played sports, was a mail man for many years walking was basically his job.
He quickly without warning signs, got a brain tumour and a heart attack and died soon after.
No guarantees in life, just try to enjoy it while you can.