Without back support, does your back feels numb after working for long hours?
Sometimes yes (and not only in the back, but also in the place where I sit). Especially if yesterday there was some serious workout that the back muscles hurt today. But in such cases, I just sit on the floor and rest my back against the wall. Or I work standing up.
This is good for those who are conscious with their health. I've seen people do this because it helps you circulate blood while standing and as we know, gaining weight through sitting for long hours is what happens for most whilst standing while doing this, it will reduce or lessen the chance of gaining weight.
Yes, we even consume a lot more calories when we are just standing and not sitting. But it is useful primarily for the musculoskeletal system, because in 90% of cases, people sit incorrectly with a hunched back or with a bowed head, etc. From this, after a while, various problems arise.
I can say that at first (if a person has been sitting in the usual way all his life) such sitting gives discomfort, but then the muscles begin to adapt to their natural work and, on the contrary, it will only be comfortable.