Oregon obesity

It surprises me how obvious a 5% difference (between 15% and 20% of the population NY vs PDX) is. When traveling from Europe to Oregon, the difference is even more obvious.
Willie Week
I wonder whether obesity in Oregon could be genetic. Some of us, after all (not me, though), are descendents of those who travelled the Oregon trail. Possibly, those that survived had slower metabolism. Possibly, those genes were passed along. 49ers didn't have as rough of a time in Cali., and Washington State has many more recent arrivals than Oregon has...so is that why we, as a population are more obese?