Depends. Is that 7 lbs of fat, water, muscle, or a combo of those things? How/why was it lost (due to diet/exercise, illness, starvation, or what)?
A person is almost certainly not going to lose 7 lbs of fat in a week, so one would assume most of that was water weight, which will easily be regained when the person is properly hydrated. It's not unusual for someone who is very overweight, to see a dramatic drop in weight early in their fat loss program, due to changes in their diet and activity.