Who says you can't have fun and get fit at the same time? According to this study regarding the physiological demand during kitesurfing, during a two hour session of kitesurfing, you can expect to shed between 1000 and 2000 calories, depending on the intensity of the activity.
As an added bonus, kitesurfing will leave your core feeling the burn for days. It can easily work your limbs (shoulders, calves, quads, glutes, etc...) unless you're already very strong. If you're not into the whole full body wetsuit thing, you could also wear some cute capris for watersports, assuming it's not bone cold.