Sorry to add to two bob a bit late but I will anyway
The best method of comparison would be kg's of fat lost (multiply your weight by your bodyfat %) as a straight weight comparison would only give net weight lost as you may lose 10kg of fat but gain 5kg of muscle and therefore only have a "weight" lose of 5kg.
Here's some info I posted earlier in the year, mainly about track fitness but may contain some useful info for someone.
viewtopic.php?f=9&t=23167Happy to sell anyone a treadmill, bike or whatever you want, at a great price of course
Feel free to give me a call/PM if you have any questions or need some info