You can be religious about that simple view if you want to. But typical gravy is 1 part grease, 1 part starch, and 24 parts liquid (stock, jus or milk). That's not a lot of grease and starch, but just enough to thicken the flavor carrying agents. Also, gravy is not a main course.
Discussion
clearly i am not religious about it since my staple food is chocolate which is a mix of sugar and fat.
and you almost certainly aren't consuming as much gravy as i am consuming chocolate.
the difference is you specifically mentioned mixing carbs and fat as the reason why something is appetizing, so i had to point out that you are in fact correct but appetizing can also be a bad thing.
there are other appetizing formulas like mixing sugar with acid that similarly lead to obesity from over-consumption.
that's the problem - that the better you get at cooking the worse you become at dieting.
ultimately diet food is unpalatable. think meat without any sauce. only salt.
and drinking only water.
as soon as you start adding spices, sauces, fruit juices and so on ... you're on a slippery slope.
food must be bland.
if you refuse to make bland food and want to cook food that normal human beings would actually enjoy eating then you must count calories.
if you count calories you can eat gravy and pizza no problem.