What Is Up With Scale Fluctuations?

If you have ever weighed yourself consistently for any period of time you will notice the scale jumps all around.

Up 1lb.

Down 2 lb.

Up 3 lb.

Down 1 lb.

Down 4 lb.

Up 2lb.

When many people go through this they find themselves on a roller coaster of emotions.

When the scale goes down they are excited, they feel accomplished!

When the scale goes up they feel defeated and like they failed….ugh!

The reason they feel this way is because they equate the scale going up with gaining more body fat and the scale moving down with losing body fat.

However your weight on the scale is representative of much more than your body fat. It includes everything on that scale.

If you stepped on the scale and then someone handed you a gallon of water, the scale would go up.

If I then asked you if you gained body fat, you would say “No dummy I am holding a gallon of water.”

This is very obvious because you can clearly see you are holding the water.

The same thing happens when you drink or lose fluids. If you weighed yourself and then drank the gallon of water (please don’t try this) and then got back on the scale you would weigh more, but not because you gained fat, it’s because you drank the water.

You can also do the opposite.

Weigh yourself, then go sit in a sauna for 30 minutes and weigh yourself again, you will be lighter. Did you lose fat? No, you just sweated out a bunch of water.

While this makes complete sense when we talk about drinking water or sweating, in reality many of the fluctuations we see on the scale from one day to the next are caused by the same thing.

Some days you hold on to more water, some days you lose more water, which causes the scale to go up or down….AND IT HAS NOTHING TO DO WITH FAT GAIN OR LOSS!!!

So what can cause you to hold on to or get rid of water?

Obviously consuming more or less water can do it but there are other influences as well.

First up is the food you do or do not consume.

When you consume carbohydrates your body stores them in your body as glycogen. However it’s not just glycogen that gets stored, for every gram of glycogen that gets stored in your body 3 grams of water get stored with it.


So now imagine this….

You have been eating low carb for a few weeks and you go out for your anniversary dinner with your significant other at a fancy steak house. You have a piece of bread from the amazing bread basket and a big baked potato with your steak and broccoli. The next morning you wake up and step on the scale and you are up 5lbs. Your immediate thought is…


In reality what happened was that most of the weight gain was you just filling up depleted glycogen stores and the water that is bound to it!

The other dietary factor that can influence fluctuations in scale weight is sodium, AKA salt. Sodium is an electrolyte that the body requires and it is critical in maintaining your hydration status. While salt has been demonized (due the excessive amount of sodium in processed foods) in reality, you cannot survive without it. The ratio of sodium to potassium helps regulate the amount of water stored in your body. When you consume more sodium than potassium water gets stored alongside the sodium around the cells within your body. This water will remain there until the balance between sodium and potassium is restored at which point the excess water will be excreted.

Here is a graph of the body weight of participants of a study where researchers manipulated their sodium intake, from low to average, to high, back to low [1].


As you can see in the graph above body weight trended with the amount of sodium consumed.

So taking our example of the anniversary dinner above, not only does the carbohydrates cause water retention but the amount of sodium can also cause further water retention. Typically in restaurants salt content is higher, so your anniversary dinner can give you a bigger bolus on salt, disrupting the sodium potassium ratio.

Next on the list of dietary reasons your weight can fluctuate is not drinking enough water. We need water to survive, everyone knows that. When we don’t take in enough water the body takes action to make sure it retains as much water as possible. It does this by manipulating levels of hormones like aldosterone and vasopressin that will then increase water retention [2]. It might seem counterintuitive that drinking less water causes you to hold on to more water, but the body is always prioritizing survival.Iit’s not going to throw away something it needs to survive if it thinks water is in short supply.

The final dietary reason why the weight on the scale can increase is purely due to the fact that you have more food in your digestive tract. You might be thinking…

“Well that means I ate more and that means I will gain fat.”

Not necessarily, food volume and weight does not equate to calories.

For example, a big plate of vegetables will have more volume and more weight than a donut, but the donut may have more calories. The vegetables will take longer to digest than the donut so it may be still in your digestive tract when you weigh yourself, making your weight go up, but in the long term, because it was less calories than the donut, you will be in better shape with the giant plate of vegetables from a fat loss perspective.

Next on the list of things that can cause the scale to go up that have nothing to do with fat gain is stress. Our bodies response to stress is generally done with survival in mind. Stress means danger to our ancient human mind, so our body readies everything in our body to be able to respond instantly to any kind of threat.

One of the most critical bodily functions that needs to be ready in times of danger is the ability to move blood throughout the body. To do this we need proper arterial pressure to move the blood to where it needs to go. In order to maintain the right arterial pressure the body needs water and salt, so it’s not going to excrete water and salt under situations of stress, it’s going to hold onto it. It does this by secreting a hormone called antidiuretic hormone or ADH in response to stress ensuring we excrete as little salt and water as possible.

Menstruating females can also experience fluid retention throughout their cycle which can cause fluctuation in scale weight. Below is an excellent figure demonstrating this from a study which followed a group of menstruating females over the course of a year [3].


In the days leading up to the start of their period you can see a steady increase in water retention and then a subsequent drop in water after the start of their period [4]. Your first thought might be that the water retention might be due to the fluctuations in estrogen and progesterone levels, however researchers did not find that connection in this particular study…

“Although there is a clear menstrual pattern in fluid retention, the peak occurs at a time when estradiol and progesterone levels are low. Perhaps there is a lag of fluid dynamics in response to previous higher hormone levels. Fluid retention around flow was similar between anovulatory and ovulatory cycles (although we had few anovulatory cycles for this analysis); therefore self-perceived fluid retention/bloating is unlikely to be due to the actions of progesterone. Although our hormone sample size was modest, there is no indication of a relationship between pooled hormone levels of estradiol and progesterone and fluid retention scores. “

Interestingly, this study on water retention in menstruating females also pointed out that those females who were active or runners had a greater amount of fluid retention than those that weren’t active.

This brings us to another important reason why the scale can increase, inflammation. Exercise is ultimately a (good) type of inflammation. It’s the inflammation that causes us to get stronger and faster [5]. Repairing the damage caused by exercise often involves diverting water and nutrients to the muscle, which as you may guess can result in the scale going up acutely after a day of hard exercise.

Lots of people can have an issue with weighing themselves due to the up and down nature of the scale. In my opinion one way to deal with the emotions that come along with these fluctuations is to take the power away from them and realize that the number on the scale from one day to the next has very little to do with fat loss or gain.

It’s more likely that the change in weight you see on the scale from day to day has to do with one of the things above. When you step on the scale each morning and realize whatever it says has little to do with body fat gain or loss it helps take the power away from the scale and realize what it really is….it’s a metric. And just like any other metric, all you want to do is log it and move on with your day. The only time you need to worry about these numbers is when you go to review several weeks worth of scale data.

It takes time to either gain or lose fat. You need to look at several weeks worth of measurements to determine whether you are gaining or losing fat. Here is an example of my scale weight over time during a fat loss phase.

If you zoomed in on a week, it might look like insanity, the number bounces all over the place, but when you look over the course of months you get a better idea of how things were trending. We all know the scale is just one metric we can use to measure fat loss and gain. It is not perfect, but in general if the scale is going down and you are resistance training and eating enough protein, then most of that should be fat loss. Could you maintain your weight or gain weight while losing fat? Sure, and that’s why we also use other metrics like measurement or just the “tight pants test”. However the scale can be a useful tool as long as you don’t let it have too much power over you.

Your mindset is important no matter what change you are trying to make. My goal with all the content I put out is for you to find the right tools to help you reach your goal. Maybe weighing yourself everyday is not for you, that’s fine. That is just one method, there are plenty more, and that’s why I provide content each week, to help you find what works best for you. To keep up to date with everything I put out on a weekly basis sign up for my newsletter using the form below.

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  1. (n.d.). Increasing sodium intake from a previous low or high … – PubMed. Retrieved February 21, 2023, from https://pubmed.ncbi.nlm.nih.gov/19173770/
  2. (n.d.). Elevations in antidiuretic hormone and aldosterone as possible …. Retrieved February 21, 2023, from https://pubmed.ncbi.nlm.nih.gov/11465231/
  3. (n.d.). Fluid Retention over the Menstrual Cycle: 1-Year Data … – Hindawi. Retrieved February 23, 2023, from https://www.hindawi.com/journals/ogi/2011/138451/
  4. (n.d.). Fluid Retention over the Menstrual Cycle: 1-Year Data … – Hindawi. Retrieved February 22, 2023, from https://www.hindawi.com/journals/ogi/2011/138451/
  5. (2019, January 7). Nutritional and Supplementation Strategies to Prevent and Attenuate …. Retrieved February 22, 2023, from https://sportsmedicine-open.springeropen.com/articles/10.1186/s40798-018-0176-6

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