Hi Sarah, I don't think there is a rule that you shouldn't weigh every day. However, it's well known that people who weigh every day are more likely to lose weight (see http://www.msnbc.msn.com/id/15234322/ns/health-diet_and_nutrition/
). Anyway, what to do with daily fluctuations? I use a spreadsheet for my weights, and have tried averaging 5 days, averaging 10 days, however the best and simplest method I use to smooth out fluctuations is to just ignore any daily change greater than 200g. So if you weigh 80kg one day, and 79kg the next, write down your weight as 79.8kg. Similarly for upwards. This is based on the fact that it's unlikely for someone to gain or lose 7000kj of fat in a single day. As for your daily variations, they don't look that big, you can always re-weigh and see if you get a different (or better) number.