I've tried sitting cross legged on the chair. It still feels uncomfortable with a little balance issue. I was spending more time in correcting my posture than sitting in a relaxed manner.
It definitely has health benefits, by restricting blood flow to the lower part of the body. It is highly advisable to eat while sitting on the floor to aid digestion
In India, we believe sitting with your leg hanging is not healthy. We usually sit on the floor which will restrict blood flow to the lower part of the body, resulting in more blood to the upper body where most of the vital organs are.
Yogis/Rishis sit for months in that cross legged posture without any issues.
Standing/Jogging/Walking is not the opposite of sitting. We need to learn how to sit properly
