I never gained a noticeable amount of weight while/after cruising.
The first one-two days I may eat more than I do at home, you know: it's easy, you try new things, you aren't hurried ...
At last, you can't eat 24/24. There's a physical limit...
I love ship elevators, I don't avoid them.
But, since I find easier than at home to go to the gym, I'm a gym lover too.
I'm a three-four days practiser on land, an everyday practiser on the ship.
I may stay there an hour early in the morning, when machines are all free, and an hour in the afternoon, mainly when the first seating starts.
I think cruise gym is a part of the fun; by the way, it's a place where you can meet cool people!