As someone from the USA who really only sees road crews from time to time, is the prevalence of obesity in construction really that high? What kinds of construction. I imagine you couldn't replace residential roofs if you were too large, forever if your job consisted of mostly ground based walking tasks like... I have no idea. But maybe some types of construction have more obese than others.

I haven't known many workers in that trade but all my experience is with thin and deceptively strong men who look permanently beat up from years of labor and small accumulated accidents.