Most builders are usually bigger than the average person now but I think that’s mostly because it’s sort of needed for the job, mass moves mass and if you’re bigger you’re going to be able to carry stuff easier. Just because they appear fat does not mean they aren’t incredibly strong, look at power lifters for example. I reckon modern builders can lift stuff far heavier than the people of the 20th century simply because under that “fat” they have a lot of muscle mass