I can only presume that most of these obese people with excellent posture were at some point (probably in their youth) physically very active. I remember my gra

I can only presume that most of these obese people with excellent posture were at some point (probably in their youth) physically very active. I remember my grandpa walking as straight as an arrow, although he was old (over 80) and fairly obese by that time. But that's because he was very athletic as younger, and still had kept a significant muscle mass although he was fat and out of shape on the first look. Proper posture simply requires that you have enough muscles that are not just strong, but also balanced in strength and length and flexibility in all directions.