Yes, to some extent that really does mean simply “more food”. It’s been awhile since people perished in famines, or the poor simply didn’t have enough to eat, but that really did used to happen. My mother remembered life before there was any form of government aid for the poor, eating just one gravy “sandwich” a day for a time. Her maternal grandparents fled Ireland during the Potato Famine, an event during which a million (or more) of people died for simple lack of food (why they lacked for it involved some complications I won’t get into here…)
For much of human history simple getting enough food, never mind the quality, was a major accomplishment and pre-occupation.
For couch potatoes and desk jockeys, yes, certainly. For people performing actual manual labor not so much.
At least these days people don’t routinely suffer scurvy by spring - that used to be a fairly common occurrence because fresh fruit and vegetables weren’t available during the winter and not a lot of cultures ate significant raw meat (which is how the Inuit avoid scurvy).
As noted - for a lot of people the “diet” might be mostly rice, or mostly potatoes, or mostly beans and cabbage - whatever could be easily grown in quantity. “Pease porridge hot, pease porridge cold, pease porridge in the pot nine days old” wasn’t just a saying, for a lot of people it was a lifetime reality. There was little variety.
So yes, the current western diet has some problems, but most subsistence farmers who go from hard-scrabble pre-modern diets to a western one suddenly start seeing their children shoot up in height. It’s a combination of adequate calories and adequate amounts of things like iron and calcium.
Natural selection doesn’t work nearly as fast as people think it does.
Although it has had an effect - the ability of some humans to continue to digest lactose past weaning, for example. Hemachromatosis, which in a typical western diet leads to iron overload, might have evolved in regions where the diet was low in iron for generations. Certain groups now prone to obesity and Type II diabetes may have evolved “thrifty” genes for putting on weight because for generations they were subjected to food shortages.
Natural selection, however, does NOT work fast enough to account for increased height from the 19th Century to present.
I think that is also a major factor.
But don’t discount the food - certain disease due to dietary deficiencies used to be common world wide and simply because we know a little more we can avoid them:
scury - cured by vitamin C, which is dirt cheap in pill form or we just know to eat some fresh fruit/vegetables once in awhile.
cretinism - cured by iodine, which is why most salt is iodinized these days, to prevent this.
rickets - that one will take some inches off your height, prevented by vitamin D and calcium
pellagra - niacin (B3) deficiency, largely gone due to fortified food like breads in the west
beriberi - thiamine (B1) deficiency, largely gone, again, due to fortified foods in the west
All of the above could stunt growth, and cause much suffering and debilitation among adults. All of the above are rare because even an “appalling” western diet provides sufficient micronutrients to avoid the above, and multi-vitamins are dirt cheap and popular, particularly for children.
A lot of this also ties into better transportation for food - things like oranges used to be Christmas gifts because they were special and expensive. We take bananas for granted - they’re common and cheap but they’re tropical fruit and are only available world-wide due to modern transportation and cooling methods. Not the most nutritious of fruit, but they contain a bit of a lot of things (including vitamins C, B1, and B3, all of which help prevent nutritional deficiency diseases) which help round out a diet. They’re soft, so they can be eaten by babies and old people with no teeth, and sweet, so both kids and adults will eat them. There are other things like that, which together add up to a much better diet than people routinely ate 200 or more years ago.
The biggest problem with the western diet today isn’t so much what is eaten but how much is eaten - the western world is obese because it eats more calories than it uses.
