Which choice sounds more natural when talking about meal or foods that are already on the table waiting for their diners.
Should it be
The meal / food is ready.
The meal / food is prepared
Technically it seems like they should be used interchangeably but in common usage you wouldn't normally hear "prepared" to mean "ready". In fact, in British English we use the word "preparation" more to describe the early stages of a task. Recipes may describe chopping of vegetables prior to cooking as the "preparation" stage before the cooking "method".
Consider these examples:
The food is prepared in the kitchen.
This does not mean the food is ready. It doesn't even mean that the preparation is underway. It simply means that food is prepared in the kitchen.
The food is ready in the kitchen.
This means that the food is fully prepared and is in the kitchen.
If you wanted to use the word "prepared" then it would be better as:
The meal has been prepared.
This confirms the preparation has been completed. But your question is specifically about which is more natural and so I have to say that "ready" is the word you would most likely hear in English.
Both sound natural, as long as you change "prepered" to "prepared", which I assume, was just a typo.
The meal is ready.
might be seen as less formal, but otherwise both examples are the same.
As a British English speaker, I'd expect either
The meal is ready.
or, more formally,
The meal is served.
The phrase "the meal is prepared" feels more like it's been translated from German.
I think the difference is that "is ready" describes a current state, whereas "is prepared" (in relation to food) describes something that happens to the food over a period of time.
To confuse this, saying "I am prepared" means almost exactly the same as "I am ready". For reasons I can't fully explain, "I am prepared" works very differently from "the meal is prepared".
My two cents:
When the preparation is done, the food is cooked. In other words, you are done with cooking. But since you mentioned that it is on the dining table, waiting for people, you better use ready.
On the market too, we have food that are ready-to-eat not prepared to eat! I may also take it this way - I prepared a burger but then after garnishing and decorating (making it presentable) with veggies around, it's then ready (to eat).
So, in short, prepared food is done with cooking, ready food is done with cooking as well as presenting to the eaters.
As a Dutchman I learned in school that the English sentence "The food is prepared" means that someone is preparing the food now, so this means explicitly that it is not yet ready. So the two sentences would mean very different things. This is a trap for Dutch speakers as a literal translation to Dutch ("Het voedsel is klaargemaakt") would mean that the food is ready. This should in English be said as "The food has been prepared".