What food we eat and how much - those are the central issues, of course, but that's not the end of the story.
Consider a few factors:
1.
Genetics. Hispanic and black Americans are much more likely to get overweight than their Asian and Caucasian compatriots. Head-to-head comparison with Finland makes no sense (as usual).
2.
How the data is collected. It's not like the NSA had a secret program for surreptitiously measuring everyone's BMI, and then some heroic/treasonous nerd leaked the results to the media. Obesity is generally
self-reported. Now, in our open (some would say "shameless") culture, saying "I am fat and ugly, and about to die of heart attack, so sue me!" is OK (outside of Hollywood and other such special zones of privilege and snobbery). There's no way your average Pole, Indian or Mexican will tell a surveyor that he is "fat"- he is exactly how the ladies like him, perfect in every way, thanks for asking.
3.
Our little friends. When we say "an epidemic of obesity", we mean it usually as a metaphor. But it just may be an apt literal description of what is happening. In the last couple of decades, a lot of evidence had been accumulated in support of the idea that both our appetite and our rates of absorption of "fattening" substances are pretty much under control of our commensal gut bacteria.
http://www.med.muni.cz/patfyz/trans/obezita/microbiom/insulin_resitance.pdf
4.
Expectations of your peers and childhood (and not just childhood) associations ("culture"):
When I came to the USA in the mid-1980s, I was absolutely puzzled: How can people who can afford (even the poorest of them) an excellent cup of coffee (just walk two blocks to the North End (Boston), four minutes - and you don't have to swallow this dishwater that pretends to be "coffee" at the Store 24) how can they drink THAT?. What's going on, don't you people have taste buds?
Speaking of "buds" - How can anyone continue to suck on the Budweiser cans when Red Hook and Sam Adams are offering vastly superior beer - at about the same price?!
And then it hit me: None of this has anything to do with taste, quality, healthiness, or what-not.
People like what they associate with great experiences of their lives. It is "your Bud" not because it is a good brew (it is a horrible brew), but because your team had won when you were drinking it for the first time, or had lost valiantly, or you don't quite remember what happened - because that was when X. had kissed you for the first time....Stuff like that.
Get real: we are not being manipulated by some evil-corporate-profit-seekers (some will try, but how far can they get, without our full cooperation?). We are being manipulated by our own infantile minds.
"Oh, my gosh, a lard-dripping, foul-smelling rotten-cabbage-surrounded pseudo-frankfurter - just like my dad bought for me at the Seattle World Fair in 1962!"
Nobody doubts your Dad's good intentions. Doesn't mean you have to devour the same "food" forever.