If eats a lot, also the letter k gets bigger

k is the prefix that indicates the 10 ³, ie the kilo-.

However, the brochure of a major pharmaceutical company would seem to suggest , “warning that
if k eats a lot, also the letter k becomes larger: k goes to K).

I’m not sure the font used is uppercase, but I think so.

But you assured, that even in systems with high calories, the value 10³ calories is still kcal (and not Kcal).