Losing 15 lbs. in 30 days is a tall order. Not only is it an impressive amount of weight to be able to shed over the course of such a short period, it also borders on an unhealthy level of weight loss. To do it, you'll have to stick to a strict regime of diet and exercise, while paying special attention to your general health.
Reduce your caloric intake significantly. Over the course of your first day on the plan, keep a diligent log of every food and drink item that you consume. Use your calculator alongside the nutritional information available on the packaging to estimate your average daily caloric intake. Reduce this figure by as much as 1,000 calories, which will allow you to lose fat at a rate of 2 lbs. per week through diet alone. Start by cutting out all junk food from your diet, then, if necessary, decrease your serving sizes at mealtimes.
Increase your protein intake. Protein acts as an appetite suppressant in those who are experiencing a significant caloric deficit. Since you're on such a strict diet, this may be a lifesaver; without cravings, you're much more likely to stick to the terms of your self-imposed eating plan. Consume at least 1g of protein per 2 lbs. of body weight daily. Protein sources include meat, fish, beans and eggs.
Perform cardiovascular exercise every day. At first, you may only be able to complete as little as 15 minutes of exercise per session. However, over the course of the 30 days allotted, you must strive to increase the duration of your sessions as much as possible to meet your goal. Since you'll be spending so much time doing cardio, select an activity that you enjoy, as long as it can reliably raise your heart rate over an extended time period. This routine will help maintain your metabolism despite your calorie-reduced diet.
Take measures to protect your general health. Due to your focus on calorie counting, you may accidentally neglect your general nutrition. Take a daily multivitamin. Make sure you get at least eight hours of quality sleep per night, and avoid alcohol.