I believe the average member of the House of Commons was visibly shorter than the members of the House of Lords at least through WWII. Certainly Americans were obviously taller than Europeans until after WWII. Even American slaves were taller and children were generally malnourished until about seven when they became capable of working. Adult height seems to have been unaffected reflecting just how rich the US was comparatively. Complete unfeeling bastards didn’t malnourish children enough to do permanent damage.
The below article makes mention of a fact that may complicate things though - big strong slaves were worth more. Presumably slave owners had this in mind so had an ulterior motive for feeding slaves better.
It’s one bleak subject.
https://www.researchgate.net/publication/11718681_The_Height...
Very bleak, but slave owners had a large economic incentive to make sure their slaves were fit for work (although that didn't cause qualms on other, more brutal forms of mistreatment). The only way they treated them well was in providing food, but that wasn't due to kindness but more from the same motivation to feed a team of draft horses well. It's tough reading, but some of the ledgers kept by plantation owners really drive the point home that they viewed slaves more akin to livestock than people. And they somehow justified what they were doing as christian and moral.
I found this interesting article while looking:
Heights across the Last 2,000 Years in England: https://oro.open.ac.uk/53774/3/53774.pdf
> Floud et al. also showed that men who grew up in urban areas were shorter than men who grew up in rural areas, and that there were significant differences in the heights of men and boys from different socioeconomic backgrounds. At the beginning of the nineteenth century, 14-year-old boys attending the Royal Military Academy at Sandhurst were nearly six inches taller than their counterparts in the Marine Society
https://core.ac.uk/download/pdf/6876106.pdf (bottom of page 101).
On top of that a knight would have eaten a lot more fat, meat, and vegetables than a peasant, who would have lived almost entirely on bread. This wouldn’t have left the peasant totally protein-starved because it was bread made from whole grains, but a knight would have been getting much better returns on their exercise throughout life due to their more varied diet.