I've been on diets and weight loss for 8 years now and in all my experience I can tell you that you can only lose 2-3 pounds of FAT per week.
A pound of fat is 3500 calories. Even losing 3 pounds is extremely difficult.
When people say they lost 10 pounds in a week it could be true but a lot of it will be water and muscle mass too
Follow the truth and you won't be disappointed