Weight Fluctuations of Fluid Shifts

If you find yourself stepping on the scale daily, or even several times a day, you’ll probably notice slight differences between weigh-ins. Try not to let this affect your mood or eating patterns as these weight fluctuations are completely normal and happen to everyone. They are most likely caused by fluid shifts, not changes in body mass such as bone, fat or muscle. The human body is composed of about 60 percent water, and depending on various factors, our bodies either retain or expel fluids.On average, body weight can fluctuate between 2 to 4 pounds each day primarily because of fluid shifts.However, those who struggle with disordered eating or eating disorders can experience greater weight fluctuations.2In this blog post we will discuss various reasons for these fluid shifts and subsequent weight fluctuations.

The first and most obvious cause of fluid shifts is the amount of water we consume and expel. Consuming large amounts of water in a short period of time can cause us to weigh more. However, consuming too much water at one time can be dangerous as it can dilute our electrolytes and lead to impaired nerve and muscle function. Sipping on water throughout the day or drinking around 1 cup of water at a time is a good way to stay hydrated. In contrast, consuming inadequate amounts of water leads to dehydration and can cause us to weigh less. Dehydration is problematic because our bodies need to be sufficiently hydrated to function properly. There are also some substances in alcohol, caffeine, and tea that increase the amount of fluids our bodies expel. Try to stay hydrated and maintain fluid balance by replacing the fluids you lose. The daily recommended adequate intake of fluids for females is around 2.7L, and for males around 3.7L.But remember, many foods and all fluids will contribute to our hydration status, not just water.

Some possible causes of fluid retention include the menstrual cycle, sodium intake, and stress. Firstly, hormonal changes during the menstrual cycle can cause various fluid shifts and it is common for women to experience fluid retention before their period.Secondly, consuming larger quantities of sodium than usual can cause fluid retention because sodium attracts and holds water.Thirdly, both physical and psychological stress can cause fluid retention because it increases the levels of the cortisol hormone, which also attracts water similarly to sodium.

Some possible causes of fluid loss include exercise, weather, and carbohydrate restriction. Firstly, it is common to weigh less soon after exercise because fluids are lost through breath and sweat. Similarly, hot and humid weather can also increase sweat production.For these reasons, fluid consumption should be increased during exercise and during the summer to avoid dehydration. Thirdly, restricting carbohydrates can cause fluid loss because glycogen (the storage form of carbohydrates) retains water. Thus, if carbohydrates are restricted, glycogen is used up and can no longer hold any water. As a result, the initial weight loss from restricting carbohydrates is due to water loss.

Chronic dieting and unbalanced eating patterns can cause greater weight fluctuations because the body is severely out of balance. If we deny our bodies the nutrients and fluids they require, it is likely that they will retain anything they get.This can create a vicious cycle of restricting, binging, and purging for individuals who struggle with eating disorders. Although purging behaviours may promote immediate weight loss due to fluid loss, it is not sustainable and a rebound effect of weight gain may occur.In addition, purging causes large electrolyte imbalances, which as mentioned previously, have a harmful effect on the body. Larger weight fluctuations not only take a physical toll on the body, but can also have a significant effect on mental and emotional states. The first step of refeeding is to properly hydrate the body, which can be particularly difficult for individuals who struggle with eating disorders as it often results in an increase in weight.6

As we have discussed, there are several reasons for fluid shifts and subsequent weight fluctuations. Everyone’s weight tends to vary throughout the day. Our bodies are dynamic systems that adapt to different environments and conditions in order to function. When recovering from an eating disorder, the initial stages of weight restoration can be difficult. However, once the body is finished establishing balance and regenerating, the weight fluctuations will diminish. If you find that your mood or eating patterns are affected by short-term weight fluctuations, try to remind yourself that this is just your body maintaining balance so that you can function optimally and do all the things you love.


  1. Stevens, J., Truesdale, K. P., McClain, J. E., & Cai, J. (2005). The definition of weight maintenance. International Journal of Obesity, 30, 391-399. Retrieved from https://www-nature-com.proxy1.lib.uwo.ca/articles/0803175.pdf.
  2. Haglund, K., Franceschi, G., & Huff, L. (2015). Weight fluctuation, chronic dieting and bulimia. In Eating disorder hope. Retrieved from https://www.eatingdisorderhope.com/information/bulimia/weight-fluctuation-chronic-dieting-and-bulimia.
  3. Dietary reference intakes (DRIs): recommended dietary allowances and adequate intakes, total water and macronutrients. In National Institutes of Health. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK56068/table/summarytables.t4/?report=objectonly.
  4. Mayo Clinic Staff (2018). Water retention: relieve this premenstrual symptom. In Mayo clinic. Retrieved from https://www.mayoclinic.org/healthy-lifestyle/womens-health/in-depth/water-retention/art-20044983.
  5. Mayo Clinic Staff (2016). Sodium: how to tame your salt habit. In Mayo clinic. Retrieved from https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/sodium/art-20045479.
  6. Winkler, J., & Alperovitz, D. (2015). The body’s response to adequate fuel in anorexia. In Eating disorder resource catalogue. Retrieved from https://www.edcatalogue.com/the-bodys-response-to-adequate-fuel-in-response-to-anorexia/.

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