Just to add, being fat takes significantly more calories than being thin. So, you really need a lot of excess food production before large scale obesity is even possible.
And we do have excess food production. We can feed the whole planet. Food supply isn't the problem, distribution and affordability is the problem.
So, that is my purely layman stab at it. I wouldn't even know where to begin doing quality research on this.
http://apps.who.int/gho/data/node.main.A904?lang=en
India for example seems low by comparison, but the rate is still up more than 20% since 1975. 18.5% for adults in 1975 vs 21.8% in 2016. Even Ethiopia the lowest country in the world is over 20.6 vs 17.7%.
> but the rate is still up more than 20% since 1975. 18.5% for adults in 1975 vs 21.8% in 2016
Nitpick: a rise of 20% on that 18.5% would make it 22.2%
Edit: I'm also not sure why the 20% marker seems to be your cutoff for "having an obesity problem". Ethiopia's famous famine went from 1983-85, yet their obesity rate for '85 is 18.7%. That seems to be an awful thin line to walk, where 18.7% marks a famine and 20% marks obesity problem.
Similarly, the Second Congo War went from 1999 to 2003 and almost 4 million people died, mostly from famine.. yet throughout that, the Democratic Republic of the Congo maintained obesity rates above 20% in your link.
For comparison US obesity rate in 1950 was 10% and considered a problem at the time now it's 35%. North Korea might not be twice that, but it seems like every other functioning country is.
PS: Ops yea, just used 18 not 18.5. But it is over 15% increase.