A person would have to eliminate 35,000 calories through dieting and exercise to lose 10 pounds in one week, an amount not considered safe, explains WebMD. A loss of 3 to 5 pounds in the first week is possible and safe through eliminating salts and starches, thus reducing water weight.
The lowest recommended caloric intake per day is 1,050 calories, and eating less than this amount can be dangerous, warns WebMD. If a person with stable weight wants to lose 10 pounds in a week by diet alone, he has to drop 5,000 calories from his diet which means he would have had to be eating 6,050 calories per day. If 6,050 calories are not being consumed per day, a person must combine dieting and exercise to create the necessary caloric deficit.
Working out each day burns extra calories to get faster weight loss. To burn the amount of calories needed for this rapid weight loss, a person would have to do high intensity workouts for several hours per day. One high intensity workout is swimming: it burns between 590 and 931 calories per hour, depending on the person's size and speed, explains Active.com. To eliminate 5,000 calories per day through intense exercising, an individual would have to exercise up to 8.5 hours each day.