You weigh yourself,  expecting to be down at least a little bit. Alas, it’s not to be today. Screw dieting, time for some ice cream. Why does this phenomenon happen? As you probably know, daily weight can fluctuate for many different reasons not related to fat loss. But rarely are these reasons quantified. So let’s do some of that now.  Understanding weighing can help with dieting, which can lower bodyweight, which can help with pain.

1. Poop

How heavy your poop is depends on a lot of stuff, including how much fiber you eat and how healthy your intestines are. Eating a lot of insoluble fiber can make you poop frequently and quickly, and eating a lot of soluble fiber can produce soft long poos. Exciting stuff. People on pain meds often have constipation, so their poos are quite different. Stress can also have an impact on poos, potentially being associated with constipation or diarrhea. How heavy are poos? The can average anywhere from a third of a pound to two-thirds of a pound, depending on different factors.

2. Pee

Most people wake up, stretch, head to the bathroom, and take a wizz. How much does this wizz weigh? Well, it can vary depending on if you woke up in the middle of the night to wizz, or if you had fluids before going to bed. Bet it probably runs somewhere around half a pound.

3. Blood

Hopefully you don’t have blood in your poo or your pee. If you do, head to your doctor! But blood volume can vary day to day. Actually, “total body water” can vary day by day. This can be due to salt intake, exercise, medications, and a host of other things. And it can lead to a daily fluctuation of one to two pounds.

4. Sugar

Your body stores carbs to be used for strenuous activity, and by the nervous system, brain, and red blood cells. It can store about 100 grams in the liver and about 300 grams in the muscles. The latter number can vary quite a bit–those who are carb-loading for a marathon can get way more into their muscles.  If you happen to eat low carb for a day or two, those stores can start to vanish.

Time for some basic math! Hold on, it’s the year 2012. That means I can’t add numbers in my head. Plugging the above numbers into an excel spreadsheet, I get a maximum value of about four pounds of body mass. That means you could potentially have a swing of up to four pounds from yesterday to today, without shedding a gram of fat mass (although it’s more likely a pound or two). What does this mean? It means, no matter how much you want your bodyweight to decrease every day, don’t hold your hopes up. Instead, consider alternative ways of weighing yourself. Measure your weight once or twice a week maybe. Or weigh yourself every day, but compare your weekly averages against each other. If the trend shows weight loss, keep doing what you’re doing. If it shows weight gain, eat less, move more, or change your diet or lifestyle to be healthier in at least some small way.


Welcome! I'm a PhD candidate researching nutrition and pain, with an MPH and MBA from Johns Hopkins and a specialty in mint ice cream and cat pictures. I'm also in constant pain from a few failed surgeries and a condition called Ehlers-Danlos syndrome, so I figured sharing knowledge would be a nice thing to do. Share these articles with pals in pain, and become my facebook friend to read more research.

3 Comments

  1. Now I get it!!! I could not understand how this could happen…I mean sometimes the scale creeps up and you KNOW the hows and whys and my thoughts on that are this: no regrets. But, of course, then I have to remedy the situation. Thank you!

    Reply
  2. Very helpful, thanks!

    Reply

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