Havto agree with the other members who've suggested that it's mostly mental. There is no universal "runner" image for the average citizen
(unless you're talking about world-class olympians, but that's a compeltely different fitness level).
For every race (a hundred to a thousand+), the entire weight/height/age gamet is represented and there are no existing opinions about anyone. What does amaze me is the
people who think they're fast and line up in front, only to be passed
within the first 100-yds. I usually give kudos to the above 70 runners as that demonstrates how many running years I have remaining.
What people need to achieve is the weight in which they feel good.
BTW, I'm 6-4, 210 and run sub-20 5k's (@ 4500'), so keep up the effort.