I think the best way is to always weigh in in the same state- always in the morning before eating maybe, or always just after lunch. If you weigh yourself at different times with different amount of food in you the results will be skewed. Losing 4lb one week is great but if you weighed after a huge meal last week then this week was completely empty the result isn't quite right. If that makes any sense! I always weigh myself in the afternoon on the same scales in similar clothes and empty my pockets!