Losing weight and metabolism

Today’s Washington Post www.washingtonpost.com/wp-dyn/ articles/A60110-2002May22.html has an article about “surprising research [that] found that levels of an appetite-boosting hormone [ghelin] secreted primarily by the stomach rise significantly in dieters after they lose weight.”

This looks like one mechanism for creating “set points,” whereby your metabolism falls (and apparently hunger rises and fat burning fall) after you lose a lot of weight.

I wonder how long this effect lasts? That is, I know there are lots of studies that say that your metabolism falls after dieting. But are there studies on how long that effect lasts? What if you keep the weight off for a year, for example?