Gamp's Law of Elemental Transfiguration

Gamp's Law of Elemental Transfiguration was a magical law which dictated the rules of Transfiguration. There were five Principal Exceptions to Gamp's Law, one of which was food.-- Gamp's Law of Elemental Transfiguration

Absit Omen interpretation

It is impossible to conjure nutritional substantive food with Wizarding magic.

This fact of life was described by Hieronymus Gamp in 1653 in his treatise that is commonly known as Gamp's Law of Transfiguration where he stated that, "no mage of any skill no matter how powerful or practiced can through spell, charm, or potion, make from nothing any sustenance."

Where Gamp's name, the date, and quote is proposed AO canon.

Duplicating food

In Deathly Hallows, Hermione says, "it’s impossible to make good food out of nothing! You can Summon it if you know where it is, you can transform it, you can increase the quantity if you’ve already got some."

It's summarized like this by the HP Wiki:

As one of the Principal Exceptions to Gamp's Law of Elemental Transfiguration, good food cannot be "made from thin air", but can be multiplied if one already has some food to multiply. -- [1]

It's proposed that AO does not accept magically duplicated food as it seems world-breaking. The same would apply to enlarged food - that there isn't more nourishment created when food is simply made bigger. Conjuring magical food article - feedback requested