There is a great difference between quick weight loss and healthy, quick weight loss.
For instance, losing 4-5 kilos in a week with shock diets do not allow you to get rid of your fats which is the basic goal of weight loss. Such diets only lead to loss of water and some muscle tissue.
Also, it is almost guaranteed that you will get the kilos you lost with shock diets.
The way for quick weight loss is; arrange your feeding habits, exercise on a regular basis by consuming more low calorie but nutritious foods.