At least in my part of the world, there is NO anecdotal evidence for this claim. I know several overweight people who certainly still don't think things through.
Now, there might be some that had a "lessons learned" some 50-100lb gain-in-weight later, and thus have begun to think long term due to the consequences they now face with overindulging and not exercising. Too many calories is rarely the reason why someone is overweight. Its usually due to lack of activity coupled with large, crappy meals and having too few of them every day. The metabolism gets shut down, thus making their body a fat-storing machine, in general.
I agree with impulsiveness 100%. This society has no spine or morale anymore and that seems to be gaining poplularity every single year. It's hard for average joe's who have not identified purpose in their life to actually follow through with being active and eating with a conscience day after day.