AUGUST, 2013 Cruises can lead to two opportunities for those focused on weight loss: a SERIOUS relapse or a SERIOUS opportunity. I was, thankfully, able to choose the later. After leaving my wife and kids in California for a few weeks while I went back to New York to work, I reconnected with my family in late August, 2013 in Seattle, where we went on a cruise to Alaska. Cruises are historically known for a place to binge, but there are a lot of healthy alternatives there as well.
The exercise rooms are pretty good. They also offer exercise classes; the “promenade” deck on large cruise ships creates a great walking opportunity, and there is often a jogging track on the top of the ship.
I made it a point to walk on the treadmill on the cruiseship about 3 miles a day. Nice, slow walk on the treadmill. Lots of fit people running. Oh well. Walk slow. Walk steady. Yes, you can lose weight on a cruise. 
Morbidly Obese to MARATHON Runner 