I know this much - one cruise we had early dinner seating, and I found my self getting hungry every night about midnight - so I ordered room service. Usually a club sandwich, with chips, and of course ice cream.
I gained more on that cruise than most.
That brings up a completely off-topic question. I gain weight when I snack at night (I generally don't even eat all day). I wonder - if I waited longer for dinner would I have less time to snack at night - and hence lose weight.
In Spain restuarants don't even open until 8:00 pm (here in Phoenix we have restaurants that close at 8:00
I was in Spain once for ship christening and we were not served dinner until literally 1:30 a.m.