I can be 163 one day, eat 1400 calories and work out for an hour, and be 166 the next. It really ticks me off! But I know that weight can fluctuate tremendously due to all sorts of factors so I don't get too disheartened.
Ever gotten on the scale at bedtime, then weighed again the next morning, only 8 hours later, and been down two pounds? Where the heck did the pounds go?
Also, I know that TOM adds a few pounds, as does too much salt, muscle soreness and ice cream at midnight.