It is very difficult and unhealthy to lose 10 pounds (4.53 kilograms) in one week. To understand why it's not likely that you will safely lose that much weight in one week, consider how many calories make up 1 pound (453 grams). There are 3,500 calories in 1 pound. To lose 1 pound of weight, you must eat 3,500 calories less than what is necessary to maintain your weight. In order to lose 10 pounds in one week, you need to eliminate and/or burn 35,000 calories and almost 1.5 pounds (680 grams) per day. This means eating 5,000 fewer calories each day or burning that much. Even if you incorporate exercise, this goal is still unrealistic.
A more practical, safe, and realistic goal may be to lose 10 pounds in five weeks. To do this, you would need to lose 2 pounds (907 grams) per week, which translates into 7,000 calories on a weekly basis. You could do this by eliminating 600 calories per day from your normal diet, for example, and then exercising enough each day to burn another 400, for a reduction of 1,000 calories per day and 7,000 over seven days. Keep in mind that you may need 1 to 2 hours of exercise every day in order to burn 400 extra calories on a daily basis, depending on the type of exercise you choose. If you're not used to exercising, you'll need to get to this level gradually to avoid straining your muscles or even injuring them.
To figure out whether or not you can afford to subtract 1,000 calories from your daily diet, first determine how many calories you need to cover normal body function and the amount of physical activity you have each day. You can get a rough estimate of the amount needed for body function by multiplying your body weight by 10. The number you get is referred to as your basal metabolic rate (BMR). For example, if you weigh 150 pounds (68 kilograms), you need about 1,500 calories per day for normal body function, including digestion, breathing and maintaining your body temperature.
Next, you'll need to figure out how many calories you need in total, considering your level of physical activity. If you know about how many calories you burn each day, just add that number to your BMR; however, most people have no idea how many calories they burn. Some weight-loss websites have calculators you can use to figure this out, or you can come up with a good, rough estimate by taking your weight and multiplying it by 14; this is about the number of calories you need each day if you are sedentary. If you are moderately active, multiply your weight by 17. Multiply it by 20 if you are very active.
Using this formula, you'll see that a sedentary person who weighs 150 pounds needs 2,100 calories per day to account for regular body function and her normal level of physical activity. To lose 10 pounds (4.53 kilograms) in five weeks, she could cut 600 calories per day from her diet and exercise for two hours per day to make up the other 400. Doing this, she could lose 2 pounds (907 grams) per week. It would be unwise to cut out more than 600 calories and go below the 1500 calories she needs for normal body function, as she could experience unwanted health effects.
There are many fad diets available that claim to offer users ways to lose 10 pounds or more per week. It's important to keep in mind that these diet plans may not work, despite their convincing sales pitches. Many of them include water weight loss in their estimates, skewing their numbers. Additionally, starving yourself to try to meet incredible weight-loss goals could leave you tired and edgy from lack of sustenance. You could even damage your body by trying to lose too much too quickly.