kencc wrote: One other point made in the book ... 75% of the weight of a human body is water and NASA assume that for space exploration the mass throughput to the human body is IN = 2.5lbs of food + 9.2lbs of water; OUT = 0.3lbs of solids + 11lbs of water. Therefore potential daily fluctuations in the human body's water total weight and water input/output have a far greater impact on a body's overall weight compared to fat fluctuations i.e. hydration may cause weight fluctuations of, say, 2lbs from day to day but a trendline will smooth out these fluctuations to give a reasonable indication of weight loss over a period of time.
Whether or not you want to use the trendline approach, just knowing the above is tremendously helpful to people who get a bit hung up about what the scales say!