Why Does My Body Weight Fluctuate So Much?

PLN coaches review body weight fluctuations, what causes them, and why you shouldn't be alarmed

Published On September 28, 2023
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Changes in body weight are common. Dieters who walk on the scale and see that they've gained weight overnight often find this to be a very discouraging and emotionally taxing experience. 

A person's weight can change by as much as 1 to 2 kilograms (2.2 to 4.4 pounds) in a single day or even over the span of several days. This can be very discouraging for people who weigh themselves frequently, such as once a day or once a week, and could lead them to seek solace in food or give up on their weight loss efforts entirely. 

While these sentiments are understandable, it's critical to keep in mind that our weight doesn't reveal everything about our health.

Why do people's weights go up and down?

Water retention variations are a common contributor to noticeable weight fluctuations. There is a direct correlation between the amount of water in the body and its weight. This has no effect on either body fat or muscular mass. 

Analysis of body fat and fluid accumulation

Body composition testing with bioelectrical impedance analysis can be impacted by water retention, just like the figure we see on the scale. (BIA). Total body water, muscle mass (fat-free mass), fat mass, and body fat percentage can all be determined through BIA testing, making it a popular technique for gauging body composition.

Although BIA testing is widely regarded as an accurate method of gauging body composition, the findings may be inaccurate if the subject has retained excess water. An overestimation of body fat mass may come from consuming water right before a BIA test. Extracellular water outputs will rise while fat-free mass (muscle mass) will be overestimated if you retain water.

If you've been dieting and/or exercising with the aim of losing body fat, seeing an increase in body fat and body fat percentage on a BIA device can be disheartening.  

It's helpful to keep tabs on your weight, muscle mass, and body fat percentage on a regular basis so that you can see your development and stay motivated. But keep in mind that even minor, unwelcome changes are possible and even to be expected along the way. Don't let them discourage you from pursuing your well-being objectives. 

Why do we retain so much water? 

Water accumulation is one of the many factors that can cause a person's weight to change. 

Between 45 and 75 percent of a person's total weight is water. Because of this, the number we see on the scale can vary depending on how much water our bodies retain.  

The amount of water that our bodies retain is affected by a number of variables, some of which are: 

  • Sodium, or sodium, is a mineral that controls how much water is in the body and plays a crucial role in many metabolic processes. Excess sodium in the diet causes fluid retention and subsequent weight increase. 
  • Physical activity: If you're not drinking enough water before, during, and after your workout, you may lose weight quickly due to sweat. However, if your water intake is higher than your water loss, you may experience weight gain. 
  • Carbohydrates are retained in the body in a form called glycogen. The process of storing glycogen involves the retention of fluids as well. This means that the higher your glycogen stores, the more water you will keep, and the heavier you may become. Conversely, a low-carbohydrate diet can cause you to lose a lot of water weight by depleting your glycogen stores, which will show up as a lower figure on the scale.
  • Before the onset of menstruation, it is common for women to gain a few pounds due to water accumulation. This occurs because of shifts in hormone levels. 
  • Medications: some drugs can increase water retention.
  • It's counterintuitive, but dehydration actually makes you keep more water. 
  • What we eat and imbibe. Most individuals tend to underestimate the weight of food and drink. After consuming a dinner that includes liquids, such as water or juice, and then getting on the scale, you'll likely find that you've put on some weight. The best time to weigh in is first thing in the morning before you've had anything to consume or drink. 
  • Use of the restroom. Urine and feces, both of which are normal body excretions, can weigh a few pounds and contribute to weight fluctuations.

How to Track Fat Percentage While Considering Water Weight 

Don't give up if you find that you consistently have bad luck on a certain day. You may be experiencing water accumulation despite your increased exercise and dietary discipline. Stay on track with your healthy eating and regular exercise, and hold off on taking another measurement until next week. At this moment, you are very likely to experience success. 

Here are some guidelines for getting the most reliable body composition test findings and minimizing weight fluctuations caused by water retention: 

Morning quiz: Morning is the best time to take the test, right after you've used the restroom but before you've had anything to eat or drink or worked up a sweat. 

  • The once-weekly test: Maintain a weekly testing schedule. Try giving yourself a challenge every Sunday or Monday. 
  • Time your last dinner the night before you weigh in so your body composition is consistent. This will lessen the chances of any gastrointestinal changes influencing your findings.
  • Keep up with your regular pre-workout routine. Either you should always work out the day before an exam, or you should always take the day off. Maintaining a consistent exercise regimen in the days leading up to the test can help prevent any water retention from the activity. 
  • Clothes.: Wear the same thing every day. The findings of the BIA test will not be impacted, but your weight may change. 
  • In general, it's best to replicate the conditions under which you took your initial body composition assessment.

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