They actually determined that because of the Winter Famine of 1945, it lowered the average height of the Dutch after the war.
Sure, thats clearly dietary. Much like the Japanese have supposedly grown since the war. Both groups have unto themselves have gene pools of just a few groups representing the majority so changes are going to be due to diet. The "average" is going to be an expression of that same genetic group fed the same things.
What is the "American" that is no longer growing in height? My comment above about local Hmongs being short means nothing because the conversation is about national average and there is no such country as "Hmong" but, its also the entirety of the real point Im trying to make.
We were and continue to be a nation that is in the plurality, according to the census, Germans. "Germans" is in and of itself something of a silly term when discussing genetics because migrating people dont recognize borders and modern borders change and for millenia it was criss crossed by warring tribes from across Europe and some from Asia leaving genetic traces. So we wind up with a group of people of a particular "German" influenced average here in The States. On the whole a taller group of people. Then various groups show up, like the relatively short Hmongs and some others. The Hmongs are now Americans. The Hmongs for the most part have kept to themselves so even if the groups have stayed genetically distinct, the average American height just got shorter.
Consider the changes in immigration policy since '65. No more Europeans, buckets from the third world. The average becomes shorter, The Netherlands hasnt experienced that.
None of any of that takes into consideration which groups from a particular modern country moved here in the past. Was there something that caused there to be a difference about a particular genetic group in one of the old countries compared to the others that allowed them to migrate here and leave the other group behind? This is something often not recognized in Americas more homogenized urban populations and I believe intentionally ignored by this kind of researcher as it wouldnt be politically correct.
So as to not draw any triggered snowflakes Ill point to non-protected groups in my area. Wisconsin, except for the urban areas, still is a patchwork of the groups who originally settled in that area and distinct genetic groups are obvious. Just to the North of me are a group of mixed Scandinavians, of that group mostly Norwegians and you can see it in them as being quite distinctly different from most of the rest of Wisconsin when you visit. The immediate area I moved to has a large group of Belgians, mostly identifying as Walloons. Amongst this group is a disproportionately large number of shorter broad men with a lot of straight dark body hair. I cant claim to have met quite the same people when I visited Belgium. Why did this particular group of Belgians come here? Were they escaping some type of oppression or were they the group that had the money to make the move? Why are they not the genetic standard in Belgium if that is where they are from? Someone else must have been left behind. There is a particular group of Dutch around here, the females in particular are short. They have no hips/backsides and disproportionately large breasts compared to other groups. I didnt meet any of this particular group of people when I visited the Netherlands but here if you meet one of these people you know shes one of them. How did that particular genetic group wind up here and not the others? According to the article, very few of this short group must remain in the Netherlands but here in the immediate area, even on a "tall" American diet, the standard for this group is short. This particular group come from long lines of farmers going back to the old country and are not the comparatively wealthy Dutch traders people often reference when talking about the Dutch moving to The States. How would the American average been effected and would Dutch be shorter as a group if this group had stayed behind?
I dont know your area so I dont know if there are any groups so easy to recognize but, Id bet that if you take a look at the recent Mexican immigrants youll see a very specific group amongst all the other "average Mexicans". This particular group is unusually short and has distinct facial features different from the others. I never bothered to try to ask what region their families were from and dont personally really know any well enough to ask but this group certainly represents a specific tribe that was localized in Mexico and now is part of us. Does this group moving here make in border Mexicans taller due to this groups loss and us "on average" shorter?
I suppose what Im really trying to get at is that the modern borders on a map may have very little to do with which genetic group lives there and that while modern politics may effect food supply temporarily modifying the height and weight of a group of people within a border, genetics has more to do with what "average" is.