This has happened before on the Korean peninsula.
If you’ve ever seen the massive armor suits worn by ancient Korean warriors you’ll notice most of them were made for men nearer to 6 feet tall for a century or more at the peak of the southern Kingdoms.
http://www.guardian.co.uk/world/2004/dec/05/northkorea
North Korea is failing to meet growth target
Robin McKie and Angela Saini
The Observer, Sunday 5 December 2004 00.58 GMT
larger | smaller
Sixty years of North Korean communism have had a grim and unexpected impact on its citizens: it has paralysed their growth.
While their cousins in the south have thrived physiologically, thanks to the comforts of capitalism, North Koreans remain as stunted in stature as they were after the Second World War. Adolescents look like children, adults like young teenagers. Nor is the height difference a slight one. After studying more than 2,300 refugees who have fled the north over the past four years, anthropologist Sunyoung Pak has found that the average young northern male is 5.9cm (2.32in) shorter than his southern contemporary. The difference for women is 4.1cm (roughly 1.62in).