So that is one difference.
But let's look at the other differences between W. Europe (this is the Europe I am thinking of at least).
1.There are ZERO local national restaurant chains in this country. Zero Chipotles, zero In-n-outs. The only national food chains are McDonald's and Burger King.
2. There are zero drive-thru restaurants. Not even starbucks. So food is not as easy to get.
3. There are fewer restaurants in general.
4. When you do go out to a restaurant the portions are smaller. I haven't weighed two things, but my best estimate is about 1/3 less. For instance, where I live, the local burrito "chain" of two locations, the burritos are about one-third smaller while the portion of chips that come with it is 60-70% smaller.
5. The food here costs more when going to a restaurant. There is no way to get a full meal for less than $10. A Mcdonald's combo meal is $15-$19. So food costs twice as much. Mcdonald's portions are not way smaller than the US, but every other restaurant's are. Because a meal is 50-100% more expensive and you get smaller portions, food is actually 3x the cost. This, obviously, has the effect of people eating less.
6. A greater percentage of people live and work in cities in Europe than the States [citation needed; would love to know the actual number]. So they probably burning 100-200 more calories a day because of this.
7. There are also zero billboards for any industry. So way less food advertising to go along with that.
These are the differences I think that make the biggest difference. There is simply less of an emphasis on food too.
But portion size, which is culture, and amount of physical activity are what I personally believe make the biggest difference.
I mentioned in another comment above that circa 2003-ish the NYT Sunday mag ran an opinion piece that proposed that gov subsidies of corn were contributing to the obesity crisis. Lower corn prices === lower price for HFCS === more HFCS in more products === more products at lower prices === more sweetener calories being consumed.
Our gut microbes aren't evolved for this type of diet.