Now the answer to the question whether quick weight loss leads to permanent results is it depends. It depends on the diet you chose. Currently there are so many diets out there promoted on TV, backed up by scientific results and yet contradicting each other. Well, think about it this way, the weight loss industry is a multibillion dollar business. Having that much financial backup you will find some scientist, who will run experiments in a way that will find the results, you want him to find. Furthermore TV and other media will declare anybody an expert that is able to sell. Combine that with a big media show and people desperately trying to lose weight and you get a magic weight loss diet.
Let's examine low carb diets for example, since they are known for quick weight loss. Basically what low carb diets say is don't eat carbohydrate rich foods or at least only small amounts of them. Now what will happen is you will experience quick weight lose in the initial phases. Unfortunately this quick weight loss will be composed of a lose of water weight depleting your muscle glycogen stores. Since muscles weigh more than fat you will go to your scale and say wow this really works great. But this is only half of the truth. Since the amount of calories your body needs every day is significantly determined by the amount of muscle mass you have, losing muscle mass means it will be harder for you to lose weight.
Let's assume your body needed about 2500 calories daily. And let's assume due to your diet you reduced your calorie consumption to 2000, which means a calorie deficit of 500 calories/ day. Now you will lose weight quite rapidly but since your using an unhealthy and unbalanced diet your losing muscle mass. As a result we assume your body only needs 2000 calories and you are consuming 2000 calories. That means you are now on a plateau. And let's face it, you'll get disappointed, you'll get frustrated and you'll overeat. But since you need only 2000 calories you will gain massive weight and maybe more than you have lost.