This calculates a 5-day average weight. You weigh in daily, and the spreadsheet smooths out the spikes and troughs that are caused by retaining and losing water. Did you know that going to the bathroom and urinating or defecating can cause you to lose four pounds? Talk about an amazing diet pitch: "Lose 4 pounds in ten minutes!" Your daily weight isn't accurate. Your average weight is a better measure of your actual weight.