Did you ever think about fact that losing 2 pounds a week adds up to 104 pounds a year? That's a LOT of weight.
Sooo.... Let's say that you have only about 20 to 30 pounds to drop. You could safely lose that extra weight in 10 to 15 weeks, or about 2 1/2 to 3 months. I think that's a pretty handy thing to know.
Why you shouldn't try to drop weight too quickly
First of all, your body tends to want to retain weight; and first weight that drops off is usually water weight, or fluid weight. So that 10 pounds that you drop so effortlessly and gain back just as quickly is probably just extra fluid.
Even if you try to starve yourself, your metabolism will just slow to a crawl, and make it that much more difficult to drop weight. Your body thinks it needs that extra fuel (weight) for survival.
Slow and Steady Wins Race
"Slow and Steady..." says tortoise.
Okay, now how do you do this?
Well, lasting weight loss means improving your eating habits and yes, exercising. This takes time and effort. This is one reason why quick weight loss is usually followed by quick weight gain - you haven't had enough time to develop good eating and exercise habits.