Losing weight quickly is often important to those who are looking to get in shape for the summer or vacation season. Weight loss that is fast does not have to mean that it is unsafe but that is one of the aspects that medical practitioners warn about.
In all likelihood you did not become overweight in a very short period of time. So it is unreasonable to ask your body to get rid of the excess weight overnight. Instead, losing weight at a rate of a few pounds per week is preferable. Doing so means the persons losing the weight is also taking care balance losing weight against maintaining health.