Liz, there is a simplicity menu on the cruise with all light offerings. They will cook anything you want that's in the ability to do - plain chicken, fish or steak are always available. The portions even on the regular menu are small. I don't recall gaining a lot of weight on an RSSC cruise to be honest. There are exercise classes and a walking track. You need to limit the alcohol and maybe have Pelegrino or Perrier more often instead.

The weight thing does need to be an entire lifestyle