As a 17-year-old, you have a faster metabolism than the majority of your older counterparts. As such, you might have to adopt a moderated version of a standard weight-loss program in order to avoid losing weight too rapidly. In order to protect your health, try to lose weight no faster than 2 lb. per week.
Reduce the caloric content of your diet. Keep a log of the varieties and quantities of food and drink that you consume over a period of several days, then, using the available nutritional information for reference, calculate your average daily caloric intake. Aim to reduce this number by a modest amount in order to avoid losing weight at an unhealthy rate. A 500 calorie deficit should suffice. Because 3,500 calories is equivalent to 1 lb. of fat, this will allow you to lose 1 lb. per week through diet alone. To reach your goal, start by eliminating all sweets, desserts and sugary drinks from your diet. If this does not suffice, reduce the size of your meals as appropriate.
Engage in cardiovascular exercise three times per week. Again, to avoid losing weight too rapidly, you'll want to keep your cardiovascular exercise program in moderation. For each session, complete either 20 to 30 minutes of high-intensity activities such as running, rowing or fast-paced sports or approximately 45 minutes of low-intensity activities such as walking or casual biking. Don't increase the frequency or duration of your sessions beyond these parameters. Slow and steady is the healthiest way to lose weight.
Complement your cardiovascular exercise program with twice-weekly resistance training sessions. While resistance training won't do much to decrease your body fat, it will allow you to preserve more muscle as you lose weight, helping to retain your strength and achieve a lean, toned appearance. At each session, perform the following fundamental compound exercises: bench press, military press, bent row, squat and deadlift. For each exercise, complete five sets of five repetitions, using the heaviest weight that you can handle without sacrificing proper form.