[ingenuous2]

I don't know what the numbers are like, but bicycling regularly increasing calorie requirements, which would have an environmental impact.

No idea how this compares to the scale of taking a bus or a solo car, but there is an increased cost. Growing food (often with fertilizers, harvest machinery, etc) in order to bring it to the market for you to consume and convert into motion doesn't seem like it's particularly energy efficient.

I bike a lot, it's better for me physically and mentally, but I do wonder how the carbon impact is affected. (Of course, this ignores the fact that petroleum is a limited supply.)

[wbl]

The main input to agriculture energy consumption is Haber-Bosh process ammonia.