Ha! I frequently swing by 2 lbs each day and sometimes 5 lbs over a 48 hour period. The once a week advice is useless for me because there's too much "noise in the numbers" to provide any guidance. Obviously it's mostly water and maybe waste product that changes. So I weigh every day but ignore the day to day changes and keep an average and only look at the trend from week to week and month to month. I wish I had some software that keeps moving averages like they do for stock prices -- that'd provide the best data. I'm no health expert, but I think everybody should go by daily average over x days if they really want to know what's going on with themselves.