6. Don’t Trust the Bathroom Scale With Your Mental Health

We humans are about 2/3 water. Each of us contains about 40 liters (or quarts) of the stuff, and each liter weighs a bit over 2 pounds. Our bodies effectively regulate fluid balance by adjusting urine output and sense of thirst, but this is done within a 2-liter range. Within this range, your body doesn’t really care if it is up to a liter above or below its ideal fluid level.

What this means is that we all live inside a 4-pound-wide grey zone, so that from day to day we fluctuate up or down (i.e., plus or minus) 2 pounds. This happens more or less at random, so with any one weight reading you don’t know where your body is within that fluid range. Your weight can be the same for 3 days in a row, and the next morning you wake up and the scale says you’ve ‘gained’ 3 pounds for no apparent reason. For people who weigh themselves frequently, this can be maddening.

There are two solutions to this problem. One, just don’t weigh yourself. Or two, defeat this variability by calculating average weights. You can weigh yourself every day, and then on one day per week, calculate your average for that week (i.e., the average or mean of 7 values). If you are really into math, you can weigh yourself every day and then each day calculate a new mean over the last 7 days. Each day you do this, you drop the oldest value and add the newest one to the calculation. And of course, there’s an iPhone ‘App’ that will do this for you.

From: Phinney, Stephen; Volek, Jeff (2011-07-08). The Art and Science of Low Carbohydrate Living: An Expert Guide to Making the Life-Saving Benefits of Carbohydrate Restriction Sustainable and Enjoyable (pp. 241-242). Beyond Obesity LLC. Kindle Edition.