I'm 5'7". My peak weight, just after college, was about 165 pounds, and I hovered at about 150-155 pounds much of my young adulthood until mid-30s. Once I started training seriously, I got down to a steady 145 pounds, +/- 1 to 2 pounds, which is still a little stocky at my height.
After "retirement" from racing in my mid-40s, I hung at around 145 until my late 40s / early 50s, then dropped about 5 pounds and have settled at a constant 139-140, which feels about right for my height. I think I look pretty fit for a mid-50s guy who isn't actually all that fit (running-wise anyway, relative to my younger self). I still run, but checked out of the "running" class into the "hobby jogging" class a decade back...
I joined the military at 18 and was a buck-twelve soaking wet at the start of basic training. Over four years of military college I managed to fill out to that peak of 165. Mostly - but surely not all - lean muscle mass.