Body Weight Fluctuation and Weight Management

Whether you’re trying to lose weight, gain weight, or stay the same, weight fluctuation can cause a lot of unnecessary anxieties. The real problem with these anxieties is that it can cause people to become obsessed with the scale in an unhelpful, and even harmful, way. Weighing yourself is supposed to be for the purpose of getting data, which can then help you make more informed decisions based on what your goal is. But sometimes if you don’t know what’s going on behind the curtain, that data can be really unsettling.

So here are a couple reasons why your weight can fluctuate:

1) Sodium

Salt makes you retain water! Water has weight to it. If your salt intake fluctuates noticeably (Ex: +/- 500mg), your body is going either retain or release water. While I can’t find any solid data saying just how much water is retained or released (nothing had any sources attached to its claims), one thing is agreed upon: Sodium will affect your weight fairly quickly.

2) Carbohydrate intake and Glycogen Storage

Your body breaks down carbohydrates into a fuel called glycogen. Glycogen is stored in your muscles (and a bit in your liver) and used to provide energy for your body during exercise. Your body stores up to about 400 grams of it in your muscles, and 100 grams in your liver (1). For each gram of glycogen your body stores, up to 3 grams of water can be stored with it. That leads to a possible fluctuation of 1500 grams of water (or ~3.3lbs in freedom units). While it’s unlikely that you’re fluctuating a full 500g of glycogen, it’s probably not unlikely to fluctuate 200-300g of glycogen, or 600-900g of water (1.3-2lbs) if you have a particularly low or high carb day!

Depending on how big you are to begin with, you can see some pretty large fluctuations. I keep my diet generally the same day to day (I batch cook things), and just this week my weight has been up and down quite a bit:

Day 1: 217.4
Day 3: 219.4
Day 5: 220
Day 6: 218
Day 7: 219.8
Day 8: 217.4

What happened? On day 2, my wife made brownies and I started eating a bowl of cereal with milk at night. So instead of my typical ~100g of carbs post-workout / pre-bedtime, I went up to ~230g of carbs. Some days though, I ate those extra snacks earlier in the day… which is likely why they processed through and I weighed a bit less the next morning.

So here’s the take-away and some advice for analyzing data for weight management:

Your weight can fluctuate based on multiple factors, and it’s really important to take those into account when assessing your progress. Weight loss is one long mathematical equation, so know your variables and you can change/manipulate it at will.


Get data!!! Your daily weight is an absolutely useless metric by itself. Get weekly averages and look for trends. Compare your weight changes with your average calories eaten.
We live in an age with an ever-increasing awareness about the importance of boundaries, thus, it makes this a great time to learn how to function within boundaries for food intake as determined by your goals! It’s ok to set some basic boundaries for how much you’re going to eat in a day (just like we limit how much we drink, TV we watch, work we do, etc).

-Analyze your weekly average for weight
-Analyze your weekly calories
-Use consistent data points

Don’t weight yourself at different times every day, wearing different clothes. I personally weigh myself in the morning, in my boxers, before I eat breakfast or drink anything. There’s no magic reason other than it’s a super convenient time for me! My morning routine brings me near the scale anyways, so in the morning is a fantastic time! Control the variables as best you can, especially the low-hanging fruit.

Get data, do it consistently, and try to get it in the same way every time. Once you get the data rolling, everything else is pretty much on auto-pilot with minor alterations here and there.

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