[jc4p]

6lb a week can easily be a large loss of water weight for someone who's overweight, it's not maintainable but if it happens for more than a few weeks in a row is the time to be worried, not now. Also, cutting 500 calories per day is a weight loss of 1 pound per week (a pound is 3500 calories) :)

Oh, and it's very possible for someone who's untrained to lose more than a pound or two a week (by being on a bigger than 1000 calorie daily deficit) and still not lose muscle but instead make new muscle and strength increases, it's just harder.

[awj]

Even if this is 1/2 to 3/4 water weight loss, that still likely isn't healthy.

You're right though, without more information to supply context it's hard to judge what is "too much".