Nice little research study in BMJ into the commuting advantage of a light frame bike vs a heavy frame. Conclusion was that there was very little difference, but seems to have engendered some discussion from his fellow medics. I like the comment that posits a  law of conservation of mass: Weight of bicycle + lock = constant.

Caution - I suspect the editors included the study (which has a population of 1!) as a Xmas entertainment, rather than for its serious research value!