A lot of people have a big loss in their first week. Many people have a big loss the week after a gain if they've pulled it back! It's amazing how quickly you can undo holiday damage!!
My biggest ever loss is 4 1/2 lb. I don't think I did anything different! I seem to have a funny pattern. 3 or 4 small losses with maybe a STS or even a tiny gain (I'm nearly ALWAYS effected by * week!) then a big loss of 3-4.5 lb! It's uncanny looking through my weight loss log because there's a really evident pattern! This is good though because it has taught me patience, so I know that as long as I'm sticking to plan, I WILL be rewarded for it, but I won't always see it every week! The one tip I would give anyone starting out is to be really patient with yourself- it's not all about one week and little losses add up to big chunks before you know it!!X