I can start that response.
It's been on the horizon and on the radar for quite some time, but we haven't had really good, accurate data until recently. Part of the data that tells us what's going on has been self-reported data, until just 2004, when the Canadian community health survey, which was done by Stats Canada, actually measured people's height and weight.
We were quite complacent in thinking that the Americans were way more obese than us because it was based on self-reported data. What we found out was that men consistently overestimate their height and women consistently underestimate their weight.