Weight management is a product of technology, as is the need for it.
We could not be the overeaters we are if we were not the inheritors of industrial farming, medicine, modern housing, energy production, and transportation.
Only a few tribes of us, like the Innuit, could have gained weight and kept it on as young "workers" in the group.
It's notable though to remember that neolithic fertility goddess sculptures found are repeatedly those of fat, wide women, indicating some sort of privileged maternity class, or perhaps more aged mothers who had multiple children and had not shed the baby pounds. Either way, it indicates fat individuals were around before we had written language.
On a personal note, when you were in engineering, was it more of a challenge to keep your gym work up? Did your desk work cause you to spend long hours at work, many tied to a static position on a computer, and eat poorly?