Move as much as possible
Go sightseeing every day. Do not waste all of your time rolling on the sand or sipping on a cocktail by the hotel swimming pool. If you go to town, do it on foot. Explore the town on your own and avoid public transport or taxi. Go on an excursion on your own. Also, if the hotel you are staying at has a gym, work out there. They may have all the necessary equipment for you: stationary bikes, treadmills, weights, etc. If not, then swim in the sea and go dancing at night. There are dozens of various options for you to choose from if you are used to leading an active lifestyle.

Drop by the local market
Local markets offer fresh vegetables and fruits. There are lots of seeds and nuts everywhere. Local cheeses, wines, meats and other products are sold there for quite reasonable prices. Stock up on your food and prepare your meals using the products grown by local farmers. Not only will you eat fresh and healthy food, you will also make friends with the local people and find out more about their cuisine.