1. Do short, hard strength-training workouts.
Focus on doing brief 15-30 minute strength training (weightlifting) workouts every other day or so. This will boost your metabolism greatly and help turn your stored body fat into lean muscle. The key is to keep the workouts short and intense. No long, boring "cardio" workouts here. Do big, compound exercises that workout multiple muscle groups... things like pushups, pullups, squats, lunges, hanging leg raises, dips, burpees, etc. For best results train in an "interval" style where you do short bursts of high-intensity exercise followed by active recovery "rest" breaks.
2. Eat slightly fewer, higher-quality calories every day.
The best way to cut calories to lose fat, yet keep (or increase) muscle, is to cut your intake of low-quality calories: sugars, refined flours, bad fats especially. You can also try cycling or shifting your intake of starchy carbs (breads, potatoes, rice, etc.). Keep your daily intake of quality protein and good fats relatively high. Get most of your carbohydrates from the best "good carb" sources: vegetables, fruits, beans, and legumes. Give yourself one big "cheat" meal every week.
3. Walk it out.
First thing every morning before eating your first meal, jump out of bed, throw on some workout clothes, and head outside for a short 10-20 minute invigorating "speed" walk. This is the only "cardio" exercise you really need. Besides ramping up your metabolism for the day and burning fat, it'll really help to jumpstart your entire day mentally and make it easier to stick to a healthy eating plan.
So there you go: a fast "natural" way to lose body fat and turn it into lean, sexy muscle tissue. Stick to these basics and you'll definitely start to see great results in as little as two weeks!