Unlike in running, performance in cycling is less dependent on body weight - with the exception of hill climbing events, and also stage racing on hilly terrain. Performance in cycling is more often dictated by the ability to maintain the highest absolute power output.
We cover this topic in a factsheet, but here is a summary of the main issues.
Example - Take a cyclist who weighs 68kg
Conclusion? Gaining power gives you back twice more in performance than losing weight! So make that your focus if you are prioritising time trialling, or criterium type races on less arduous terrain.