Back in the day (late 1980s/early 1990s) when I was bicycling twenty or thirty miles a day three hundred days a year (and playing guitar at the same time!), I was about 140 to 160 pounds. Those days are long gone. I've been 190+ for the past ten years now, but I hope to bring it down some by eating healthier and riding my bicycle a LOT this summer (while playing guitar at the same time, of course).
About three years ago when I started riding again after a break of some years, I definitely noticed that the center of gravity of the bicycle/rider/guitar system had shifted upward due to my increased mass. This made riding with no hands while playing guitar a bit dicier than before, but the advantage of tens of thousands of miles experience compensates for it. I've gotten used to the shifted c.g. in the past year or so where I don't even notice it anymore, but it was a shock back in 2005.