I am 6'2" and weight 250.  I am not "thin", but I don't have a large beer belly either.  In most Carhartt clothes I wear a XL tall.... in the past when I purchased carhartt thermal under wear (tops and bottoms) I had to step up to a 2xl tall as those cotton based items tend to shrink.  When I purchased a new union suit, I thought a 2xl tall would work for me - however, it was "skin tight".  I had to exchange it for a 3 xl tall - this fits me comfortably, it is not "baggy" in the chest or waist area - maybe a little baggy in the butt.  I don't like the buttons - wish they would come up a zipper or even velcro or snaps?  I have worn this a few times and it does keep me warm - just be aware of cotton shrinkage.