Originally Posted by
mr_pedro
I do see big heavy guys doing 20+ mph on flats, but they are never fat. Next to impact on aerodynamics, excessive fat must also hurt the ability to produce large amount of power for long time on bicycle. Maybe because it becomes very difficult to remain stable in the saddle while doing 90-100 RPM.
I suspect that two other reasons play more of a role.
1) Not all riding is done where the terrain is flat and riding up hills is much more difficult with excess weight. That makes bicycling far less enjoyable for those carrying around lots of extra pounds without corresponding muscle strength. As a result, these individuals will be under represented in the cycling population.
2) If you do much riding at 20+ mph, even on flat terrain, you're burning quite a few calories therefore making it less likely that you'll be gaining much weight (and more likely that you'll be losing some if currently overweight).