If you already have a significant amount of weight to lose (50 pounds or more), you can lose up to 10 pounds in one week by following strict dietary guidelines and a cardio workout regimen. Drastic changes in your regular lifestyle, specifically aerobic exercise and a sharp decrease in calories, causes fast weight loss. The hard part is maintaining your weight loss.
The Centers for Disease Control and Prevention reports weight loss is best achieved slowly and steadily with a program that includes physical activity. Losing one to three pounds per week is a healthy weight loss goal for most people.