Why Does My Weight Fluctuate So Much?

Why Does My Weight Fluctuate So Much?

Have you ever stepped on the scale on a Sunday morning and thought “Holy Sh***t I really blew all my progress this weekend”. Or even on a random Wednesday, seen a big spike and felt discouraged because you were consistent with your exercise and nutrition all week? Does the scale feel like random numbers to you and lead to frustration?

The scale is a great tool to measure weight loss but the truth is, there are nuances to why your weight fluctuates that aren’t all about fat loss or gain. In this article, we’ll explore a few reasons how water actually impacts your short-term weight the most.


Table of Contents

What Causes Daily Weight Fluctuation

Reasons Water Impacts Weight Fluctuation

Moving Forward & Next Steps

Summary FAQs

What Causes Daily Weight Fluctuation?

Long-term weight trends can be explained by energy balance (calories in vs. calories out). If you intake more calories than you burn, your weight will go up and vice versa.

However, in the short term, we have all witnessed the scale go up and down in a single day that can’t be explained by pure fat/muscle gain or loss. Sure, if you pound a case of beer and eat pizza for all three meals you will gain some fat. However, one day of letting loose won’t have a large impact on body composition.

A pound of fat is equal to roughly 3,500 calories so in order to gain that in a day you’d have to eat that amount on top of your normal maintenance calories. That’s not easy to do!

So, how can you hop on the scale and see a 5lb increase the day after Thanksgiving?

The main reason is due to water.

Fun fact: humans are made up of around 50-60% water. Your organs, bones, etc. are all mostly water. And water has zero calories. Step on the scale and weigh yourself. Now drink a liter of water. Go back on the scale. It’s higher. Did you gain fat? No, of course not. But you did gain weight which is completely normal and nothing to worry about.

Reasons Water Impacts Weight Fluctuation

Here are a few reasons how water can both, directly and indirectly, cause weight spikes and drops.

Carbs and Salt

If you ate more salt or carbs than usual the day before you may have an increase in weight. In regards to salt (sodium chloride), your body will retain water which can cause bloating and an uptick in weight. Water molecules bind easily to sodium to help maintain fluid balance.

For carbs, it’s a very similar process. Carbs are stored in the body as glycogen. Glycogen molecules are filled with water and stored in your muscles and liver. Therefore, the more carbs you have, the more water weight you retain. Again, this is not fat loss or gain. It’s simply water weight!

This is why the opposite will happen if you eat less salt or carbs. Your body will flush a lot of weight quickly. These foods don’t inherently cause fat gain, they hold onto water more than other foods which shows up as short-term weight increases.

This spike in weight can look even more dramatic if you’ve been limiting carb intake through something such as the keto diet. The first few weeks of a low-carb diet look extremely promising because you lose weight so quickly. These are results are deceiving because it’s not necessarily fat loss, but rather your body flushing out water weight that would have otherwise been bound to the glycogen.

Timing of weigh-in: late meal or early weigh-in

If you are someone who uses a scale, making sure to weigh yourself at the same time of day will help achieve more accurate data. If you weigh yourself earlier in the day than you typically do, your body has had less time to digest the food from the night before and the scale will likely show a higher number. Same thing if you ate a meal later than you usually do. Digestion time is shorter than if you had eaten at your standard time and the scale may reflect that with a higher weight.

This also ties into weighing yourself under the same conditions every day. If you typically weigh yourself first thing in the morning without having anything to eat or drink and then weigh yourself mid-afternoon after a few meals, the number on the scale will be quite different. To keep the variance at a minimum be consistent with the conditions you’re weighing yourself under. Stick to the same time of day, before or after meals, and with the same amount of clothes on or off.


This probably isn’t on the list for the reason you think it is. When you’re stressed your body releases cortisol which some claim leads to weight gain (specifically around the midsection). Cortisol is your body’s main stress hormone and is best known for triggering your body’s fight or flight response. There’s no strong evidence that the amount of cortisol produced by a healthy level of stress causes an increase in body fat, however, you can experience short-term weight gain from higher cortisol levels. When cortisol levels go up (like when you’re stressed) your body will retain water and your weight will temporarily increase due to that water weight. This is why people sometimes see a big weight drop when they stop dieting and move into a reverse cut. When their body loses the stress of dieting it releases the water and looks like a big drop in pounds.


You might hop on the scale after a really tough training session and see a jump in weight. No, you didn’t gain 3 pounds of muscle overnight (though how great would that be?!) but when your muscles are damaged they absorb nutrients and store more glycogen to recover. This will show a short-term weight gain. The same goes for after a rest day, you might weigh less because your body isn’t storing this for recovery.

Food in your Stomach

This reason isn’t water-related, but if food is sitting in your intestines and you haven’t gone to the bathroom yet, you’ll obviously weigh more than if your stomach was empty. We will leave it at that.

Moving Forward & Next Steps

So what do you do with this information especially if weight management is important to you?

  • Stay hydrated. Water is important and you should never sacrifice staying properly hydrated to manipulate an arbitrary number on the scale.
  • Understand weight doesn’t equal body composition. The number on the scale doesn’t tell how much of it is fat, muscle, water, etc. Use the number as one data point and try to not over invest yourself in the number. If it does impact you emotionally, you don’t need to use the scale at all.
  • Understand your consumption. People are notoriously bad at estimating their food intake (most people underestimate). Long term calorie tracking isn’t for everyone, but you should try it for two weeks to learn what you are actually putting in your body.
  • Be mindful of your weighing frequency. If you do track your weight, step on the scale under similar conditions every day and monitor the average rolling number. Pay more attention to monthly and yearly trends to avoid yo-yo dieting and other extreme and destructive behaviors
  • Be patient
  • Keep drinking water
stock market

Treat it like the stock market! Of course there going to be days where the market dips. Would you pull all your money out and quit investing in your IRA? Absolutely not. As long as you are headed in the right direction on a monthly or yearly basis, keep going!

Summary FAQs

Can You Gain Weight in One Day?

Of course, but it’s most likely going to be bloat and water weight. Your body does a good job of regulating itself and will bring it back down to typical levels. It’s likely you can gain some fat, but nothing to worry about. Unless you are having a historic cheat day, you’ll be fine

How Much Does Weight Fluctuate?

It’s not uncommon to see 5-7lbs of fluctuation in a day. It all depends on when, what, and the amount of what you’re putting in your body, exercise, and sleep.

Why Do You Weigh Less In The Morning?

We weigh more at night because we have eaten and drank all day long and our stomach is full. During sleep, we are still metabolizing food and burning calories at rest

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Brooks Hurbis also has a fitness business if you are looking for more personalized online coaching. You can find her at https://www.sweatsimpleco.com.

Tips for Getting Over Gym Fear

Tips for Getting Over Gym Fear

When you’re just beginning your fitness journey the gym can be an intimidating place. From the large assortment of machines that you may not know how to use, to the people lifting heavy in the back and grunting, it can be enough to deter you from starting any resistance training. In college I was so scared of the weight area that I just did the elliptical on repeat. Not exactly what you’d call a well-rounded training program. If your fear of the gym is holding you back from resistance training here are some tips to get you feeling more comfortable:

Come with a plan

Knowing exactly what exercises you’re doing and how to complete them will make you feel more confident and less out of place. If you’re unsure how to execute an exercise, leverage resources like a trainer or YouTube videos that show proper form. Do your research ahead of time so you’re not trying to watch videos in-between sets. If you’re still feeling uneasy about a certain exercise, practice a few reps at home so it feels more comfortable on your body once you get to the gym.

Know your equipment

Before getting to the gym, make sure you know all of the equipment you’ll need for the workout and how to properly use and adjust them. YouTube can be another great resource here if you don’t want to approach your gyms staff. If barbells scare you, start minimal! Bodyweight and dumbbells can be a great jumping off point for those new to exercise. When I was first starting out in the gym I would bring all the equipment I needed to one area so I could zone out in my small space and not worry about what else was happening around me.

Remember that everyone was a beginner once

Yes, even that guy grunting and lifting twice his bodyweight had a first day in the gym. The only way to feel more comfortable and get more seasoned is to keep going. Everyone has to start somewhere and everyone there is working towards their own goals. Though it may feel like it at first, no one there is paying attention to you attempting your first hip thrust or skull crusher. Remember why you’re there and that it’ll get more natural each time you step onto the floor.

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Want to level up your fitness? Check out the workout programs we offer! All profits go towards raising money to cover the expense of teachers’ classroom supplies.