What are the criteria that constitutes a "healthy food"? This is not a
philosophy question. I am opening a restaurant, and it will cook food
right in front of customer and customers would simply take it to go.
Obviously, it is "fast-food".

So, is "fast-food" neccesarry mean unhealthy, junk food? Can
"fast-food" be a healthy food that people cooked at home?

So it goes back to my questions, what criteria do I apply to determine
whether this dish is healthy?

Please be as specific as possible. Thanks

Just a quick comment....  I believe that you are asking about
healthful food.  There really is no such thing as healthy food (just a
commonly misused phrase).  Perhaps, understanding the difference
between healthful and healthy (and advertising to your customers)
could be a selling point for your new restaurant.  Best of Luck!

Well I mean a healthy diet. See, I am not planning to use "healthy
food" as a selling point. I believe that my targeted consumers should
recieve a healthy food by default. I am asking for a strict guidelines
so that when we come up with new menu we can say, "according to the
guideline, we believe this is healthy".

It is same as defining company's values and visions. When situations
come up, we can then compare it against the values and visions and
ask, "does it conflict with our defined values and visions?".

So same here. I want something that I can ask myself, "Is this healthy
according to our defined healthyu-diet guideline that we establish?"

Thanks!