I actually saw a scientific explanation in the in-flight magazine of one airline I flew (I think it was Asiana--it was several years ago). It's related to the air pressure in your stomach versus the air pressure in the cabin, at least according to the explanation. It had a little cartoon man with waves emanating from him...I really wish I'd stolen and saved it!

Now, if yiu could prove that there is more gas generated on a CX flight than other airlines, THAT would be a topic worth exploring here--otherwise, you'll probably get a free ticket to TravelBuzz momentarily (and some more interesting responses there too, if there isn't already an existing thread!)