I’m not just talking about weight. I’m talking about total height and bone length and all that. Seems to me that’s changed and I don’t think I’d attribute it to nutrition.
My dad is 6' but had rickets as a child because of poor nutrition. If he had not he would have been somewhere around 6' 3" or taller. His brothers tended to run around 6' or slightly under with the older brothers, (who were born when things were very tight) being shorter then the brothers who were born later.
All of their sons are over 6' with some reaching 6' 6".
In Chile you could tell who was born when by their height. Those who were born before 1965 were quite short, those who were born between 1965 and 1975 were taller and those who were born after 1975 were quite a bit taller.
The reason?
In 1975 the government began giving each family with children under five a generous ration of whole powdered milk. More protein, more fat, more nutrients in the family's diet lead to taller children with greater bone mass.
Every time there is a change in diet whether greater nutrition and calories or less the average size of the people in that area either grows or shrinks.