It's best to just weigh yourself only once a week, the same time and day every week, wearing the same thing (or nothing at all if possible). I had the same problems in the past and actually had to put my scale away between weighings to keep myself from getting on and possibly feeling disappointed. You spoke of The Biggest Loser...they only weigh once a week. If you must weigh on other scales at different times, only count yours for your main personal records.