Why Does My Weight Go Up and Down??

Why your daily weight fluctuations don’t matter as much as you think

First off…

Your weight is a measurement of gravity’s pull on you to the earth.

NOT a measure of your self worth or any other nonsense like that.

Your weight can be heavily influenced by many factors on a day to day basis.

For example, your weight can fluctuate based on sodium levels, food in your gastrointestinal tract, glycogen levels, menstruation (females), etc. But let’s break those down…

Sodium Levels:

Have you ever eaten a really salty meal and then felt completely bleh after it? That’s not just in your head. When you consume salty foods, your body retains water at higher levels than normal. Since your body is retaining more water than normal, the water you consume stays in the body for a longer period of time. So… when you hop on the scale the next morning after that big salty dinner you had, you might see a weight spike from that water you’re holding on to.

Food in your GI Tract:

When it comes to actual fat loss, the time at which you eat your meals has no effect on your body fat %. However, it might have an effect on your scale weight. Picture this – you come home from a long day of work and didn’t have the chance to eat all day until right before bed. You go into the kitchen and eat a big heavy dinner, you brush your teeth, slide into bed, and wake up the next morning ready to hop on the scale and… three pounds heavier than the day before. Did you really gain three pounds in one day? No. You just had a couple pounds worth of food and water right before bed that your body hasn’t had a chance to flush out yet. Remember, if you get on the scale weighing 120lbs and then drink 16oz of water and get right back on the scale… you. will. weigh. 121lbs. ~Math~.

Glycogen Levels

Real quick and very simplified for the sake of this article – glycogen is the primary source of fuel that your muscles use whenever you work out. Keeping that in mind, when you eat carbs, your body undergoes a process where it converts the carbs into a useable source of fuel (glycogen). When you eat a high carb meal, your body starts to convert those carbs into glycogen. Whatever glycogen that doesn’t get used up quickly becomes stored in your muscles and liver for future use. Each gram of glycogen carries three grams of water with it. So how does this relate to your scale weight? When you consume carbs your body needs water to tag along with the glycogen those carbs create. As we now know, more water staying in the body, more weight on the scale.

Important side note: Ever wonder why your friend who cut carbs out of their diet lost 5 pounds so quickly!?!? No carbs -> less glycogen -> less water in body -> lower scale weight. Cutting carbs didn’t magically make your friend lose 5 pounds of fat overnight and now you know why.


As a female reading this, you’re probably thinking “Oh great some guy is gonna mansplain why I gain weight on my period”. Fair point. You probably know how much weight and why you gain that weight on your period and I’m not going to try to explain that to you. But let’s assume your’e somewhat curious as to the why behind the weight.
Long story short, hormonal levels effect your body’s level of water retention. When your period is coming up, the body’s levels of estrogen and progesterone drop. When these hormone levels start dropping, it can signal your body to start holding onto more water than normal. As we’ve learned time after time… more water staying in your body = higher weight on the scale.

Now are you starting to see why your weight on a day to day basis is not of great concern? Great.

Weight is a great way to track progress long term by looking at the way your weight trends up or down.

If your weight trends downwards over the course of a month, then yes you’re most likely predominantly losing body fat.

If your weight is trending upwards over the course of a month and you’re strength training and eating adequate protein, then yes you’re most likely predominately gaining muscle.

The big takeaway is how your weight trends over time, so DON’T get wrapped up in what the scale tells you each morning.

Let’s look at my weight graphed out over the past week:

I started the week at about 168 pounds and by Wednesday I was down to just under 165 pounds. Did I drop 3 pounds of body fat over the course of two days? Of course not.

What you’re seeing in action above is the power of all the different things that can impact your weight throughout the week. If we follow the thru line of data here, I pretty much maintained my weight throughout the week.

BUT, if I weighed myself on Wednesday and saw 164ish and then on Sunday saw 167ish AND didn’t have the knowledge we’ve gone over in this article, I might have thought I gained 3 pounds of fat in just a few days. But now, you’re smarter than that. You know that any number of things could have caused that three pound swing.

Remember, that the scale changes day to day and if we look at just a few data points in isolation, they can be cause for panic. My hope is that this short article gave you the toolset to recognize why we should trust the trending direction of your weight, and not your daily weigh-ins.

So, what are better ways to track your progress other than scale weight? I like to have my clients take measurements of their body, take before and after photos, and note how their body looks and feels to them. At the end of the day, most of us aren’t yearning for a specific number on the scale. We’re yearning for the way we will look, feel, and move at whatever scale number we have in mind.

I’ll say it again because it bears repeating:

Your weight is a measure of gravity’s pull on you to earth. NOT a measure of your self worth.

If you found this article useful, I’d love for you to share it with someone you care about and if you’re interested in putting this info to use with me in a more hands-on manner, you can apply for online coaching here.



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