My 2p
I first read about this years ago in the book Fit For Life, by H and M Diamond.
They claim that a 24 hour day is divided into 3 eight hour periods. I can't remember exactly, but I think that midnight until 8am is when the body is eliminating toxins, so should not have to divert any extra energy to digestion.
Personally, I think that's a bit far fetched, but who knows? There may be a grain of truth in it.
I certainly feel better if I avoid a heavy meal late in the evening. Munching a piece of cheese is guaranteed to make me wake up feeling bloated and tired.
I believe that the best type of food for a late night snack is fruit. It is easy to digest and low in calories.
Fruit also makes an excellent snack at any time of day, including breakfast, although it should always be eaten BEFORE a meal to allow the meal to be digested properly.