A misconception (helped by a multi-billion dollar weight loss industry) is that it's possible to reduce fat in a targeted part of the body, especially the part where fat is most attracted - the belly. To lose belly fat you need an all round exercise routine that lowers fat levels throughout the body.
You need to eat healthier (more vegetables and fruit), more often (don't starve yourself) but smaller portions.
Drink more water and reduce sugar intake (sodas, milkshakes, cookies etc.) and eat more fiber.
Exercise cleverly - crunches might work your ab muscles (if done correctly, if not they can actually cause stomach bulge) but the exercise doesn't actually burn enough calories to lose a significant amount of belly fat (even if you did thousands daily).
You need full body workouts (like swimming) that burn the most calories and kick start your metabolism.
For someone who really knows how to lose belly fat I suggest you visit truth about abs and flat stomachs it's the top abs program on the internet.
Exercise has many advantages and once you get into a routine you will find a reduction in your stress levels and you will sleep better - good for your metabolism and general well being.
Good luck for the Oscar 