I go by what my gym scales say (tho I do admit that last week I took my shoes off to see if it made a better result!). I find I just get far too attached to what they say and get really down if I know/feel that I've lost but my scales say STS or worse, a gain! At the moment they are sitting in the bathroom gathering dust as I just refuse to be influenced by what they say - the gym ones are really accurate and I'm happy to have whatever they say recorded on my gym sheet, rather than get the hump and moan that my scales at home say less (which I would!)