Hey there robert333,
we seem to have had a similar year. I'm 20 years old and an undergraduate. I packed on about 20Lbs this year, and have intended to lose it since the beginning of summer (now long gone). But I truly am ready to get on track now... I refuse to start 2009 like this, making some lame new year's resolution that next year will be different. Instead I am making an October resolution to be 150Lbs by the end of December lol. That's about 10Lbs a month.
Anyways, I disagree that 5Lbs is too much to lose in one week. When I first start a diet I lose the first 10Lbs really fast, I assume its mostly water. I read in a biology textbook that the average adult has 5-20Lbs of food in their digestive track... gross eh! Between that and water fluctuations your weight can change dramatically without actually losing fat. After a couple weeks of eating healthy though, I agree 5Lbs a week would be quite high.