My advice to you would be to challenge yourself to enjoy the the activities and the people around you. Prove to yourself that you do not need food to make you happy. HOWEVER, let yourself enjoy a bit of a treat here and there. I'm assuming the cruise is all-inclusive... For drinks, drink white rum with diet pop...it has the least amount of calories. For food, choose things baked, not fried and desserts that are less on the creamy side and more on the fruity side. All the food is going to be delicious, so take the healthier options! That would be my advice...but most of all just enjoy the company and the sites around you.