I also try to limit gluten in my diet. So, when we're traveling all I do is lay off the breads, rolls, danish, etc. and actually this is easy to do on St. Martin. Many of the restaurants have excellent seafood offerings, and I usually focus on that. If you like lobster, grouper, etc. you'll find no shortage of it on SXM. And, it's all 'gluten free!'

As far as doing stuff inland, I agree with all the suggestions above. Having a day or two away from the beach can be a nice break. If you like shopping Philipsburg and Marigot will have plenty of that. Unfortunately, the zoo and the butterfly farm were wiped out by the hurricane 16 months ago, but Parrotville has re-opened and is worth a visit. Not sure if the Yoda Guy is back in Philipsburg, but his little Star Wars museum and gallery was also a nice break (and it was air conditioned).

Can't help you with a workout program, but one thing my wife and I do when we visit Orient Beach (or any other beach that's long enough) is that we love to walk the shore from top-to-bottom. It keeps us moving and helps burn off all the food we've been consuming during our stay! And, Orient Beach is one of the best for this. It's about 1.3 miles from the northern tip near Mont Vernon all the way down to where Papagayo's used to be in Club Orient. So, round trip we would log about 2-1/2 miles with each walk. But, if you're thinking about strolling this in the 'buff' you are limited to the beachfront below the rocks where Pedro's used to stand. And, I wouldn't worry too much about how you look with or without a suit on. From my past experiences no one really notices or cares, and everyone there is happy just to be on vacation. Good luck.