Do the best you can but it is really impossible at dinner. The wife and I went on a cruise in August and I was able to do good at the buffets but the dinners are impossible as the waiter will bring you desert even if you tell them not to. Of course you can just not eat it but once it is in front of you it is pretty tough not to eat it. Most nights they will bring you two or three deserts. I was able to pass on the carbs that came with dinner(potatoes, rice, bread, etc.) other then the deserts. It was a 7 night cruise and I ended up gaining 5 lbs. It took me two weeks to get back to my pre-cruise weight so it basically set me back three weeks.