He told us unequivocally that his generation was noticeably shorter. Some searching turned up lots of mentions of malnutrition on pacific islands when local diets were disrupted, though it's not so easy to find mentions of Yap specifically. Here's one mentioning the Marshalls.
What I'm saying is that food can have bad consequences in terms of cancer or heart health but not necessarily stunt growth. The unhealthy American diet (tons of sugar, salt, meat and animal fat) is not known for stunting growth, and your evidence for it is more than thin: One sentence in a book written by someone with a degree in political science.
American diet is not exactly a cherished notion of mine either. Neither is it my diet of choice nor am I American.
Stunting affects about 147 million children worldwide.
This long term under nourishment is very common. The WFP (world food program) gives estimates of 227 million for Africa and 553 million people in Asia and Pacific.
What happened when local diets were disrupted? Were local foods bought in return for much lower quality food? Was malnutrition made worse? Or did we just start documenting it better?
http://books.google.com/books?id=p3liL6fAjrcC&pg=PA83&lpg=PA...
I suspect you are protecting some cherished preconceived notions.