1. Eat a Very Simple Protein-Based Diet
Eat a simple diet based around natural, unprocessed whole-foods. Protein should be the focus because it revs up the metabolism, stabilizes blood sugar levels, and helps to suppress your appetite naturally. It also contains the amino acids your body needs to build/repair muscle tissue. Also include plenty of unprocessed "good" carbs (veggies, beans, small amounts of whole grains, fruit, etc.) and a small amount of healthy fats (olive oil, natural peanut butter, unrefined coconut oil, etc.).
2. Do Full-Body Strength/Cardio Combo Workouts
Do short, full-body workouts based around strength/resistance training and interval cardio (like HIIT). You'll burn more calories and fat while protecting and toning that sexy lean muscle that keeps your metabolism boosted 24 hours a day. Focus on keep the intensity levels high and workout no longer than 30 minutes at a times. Do 4-6 of these workouts per week, depending on your fitness/conditioning level.
3. Drink LOTS of Water
Try to drink about a gallon of pure water per day. This is a little trick used by bodybuilders and fitness models when they need to lose fat and lean down fast. The large amount of water, consumed bit by bit over the course of the day, will do lots of good things for your metabolism and appetite control. It will also allow your body to flush out toxins that get released during a rapid weight loss program.
There you have it: the fastest way to lose 15 lbs by the start of summer. If you stick with this simple plan you'll have no problem burn off ugly fat and building that sexy, lean "beach body" within just a few weeks. Good luck and leave your questions/comments below!