I've lost nearly 100lbs (250-160ish) over the past ~13 years simply by being more aware of what I was putting into my body and gradually consuming less. I wasn't really taught that excess caloric intake = increased body fat when I was a kid and I guess no kid really should. Parents need to be taught so that they can be that health-buffer.
Over the past few years I've been incorporating more exercise and I intend to start a bit of weight-lifting before I hit that age peak where performance drops off. I figure it's an investment into my body that will pay off in me being more mobile should I make it to old age. I've elders in my family that have different levels of fitness at around the same age (say, 60s-70s) and the gap in quality of life is astounding. I do NOT want to be feeble or immobile in my late 60s-early 70s.
Naturally, I'm also self-conscious/narcissistic and want to work myself to a good 'bod' while I still can. Sure, societal pressures drive this a bit, but I don't think it's harmful to my sense of self-worth. Basking in the glory of a six-pack would just be the icing on the cake of my being.