One pound of body fat is equal to 3,500 calories, according to the Mayo Clinic. To lose 9 lbs. in 11 days, you will need to lose a total of 31,500, which is equal to approximately 2,864 calories every day. To lose those 9lbs., you will need to maintain a strict diet and participate in physical activity. While losing this amount of weight in such a short amount of time is possible, you will need to do considerable amounts of exercise to make it work.
Determine how many calories you will burn through diet and how many you will burn through exercise. Reduce your diet by 1,000 calories and burn 1,864 calories through exercise to create a deficit of 2,864 calories a day. You can adjust these amounts as necessary.
Spread your daily calories through three meals and two small snacks. Each meal should count for approximately 25 percent of your daily calorie needs. Split the remaining calories between your two snacks. For example, if you are currently eating 2,500 calories a day, you should eat 1,500 calories. Eat three 400-calorie meals and two 150-calorie snacks each day.
Use cardiovascular exercise to burn at least 1,864 calories per day. According to ShapeFit.com, an hour of step aerobics, swimming the breast stroke, bicycling, racquetball or rock climbing will burn about 800 calories while an hour of running, the elliptical trainer or rowing will burn about 600 calories. Mix and match your favorite activities, for example you could bicycle for an hour, swim for 30 minutes and run for 67 minutes to burn a total of 1,870 calories.