I always order a vegetarian meal. Actually, I like to try different kinds: Indian vegetarian, Jain, vegan. They are always much better (to me!) than the regular meals.

One of my first times flying J class, the FA came up to me and apologized- he said he had never seen a special request meal with so little food. He said this to me before he served it. Then he apologized again as he served it. I forget the details- I think it was a breakfast meal, as I remember him offering boxes of cereal and a banana to "supplement" it. The thing is, it was fine for me. I am a big eater, so it might have been the excitement of finally flying J, as the FA did not think it was standard.

A few times after that (also in J), I would be served the first part of the meal- a salad and/or fruit, typically, and think (as I looked around at the "regular" meals that appeared to have a lot more food) "hey, is this all I get because I ordered a special meal?" Then I remembered, relieved, that the salad was just a starter. Most of my flying career has been in Y, where they serve just one "plate", until recently.

These have all been international flights. Once, on a connecting flight in the US (arriving from Y class international), I was in first class, and served a "regular" meal. I informed the FA I had ordered a vegetarian meal, and was told that that option was not available on that flight. I was surprised.

So, no, I have not had that experience of having an inadequate amount of food (although the FA thought so!), but I have worried about it!