Why Does Our Weight Fluctuate?

It’s a moment of panic most of us have experienced – stepping on the scale and seeing a number that is higher than expected. No, the scale isn’t lying (although we like to think it is) — but luckily, these daily, and sometimes dramatic, weight fluctuations can be explained and they often have little, if anything, to do with fat gain. Let’s take a look at some of the main causes of daily weight fluctuations…


  • Sodium: Significant changes in this electrolyte that result in weight fluctuations. If you suddenly consume more sodium than you are used to, you will likely retain water. Conversely, if you suddenly consume much less sodium than normal, you will release water. Ideally, its best to try and keep sodium intake constant. Note: you should not be avoiding sodium!
  • Fibre: Soluble fibre absorbs water and expands and stretches the stomach, which makes you feel full as it slows down the movement of food through the stomach and small intestine. This can cause bloating and water retention as a result.
  • Food: The food we eat every day weighs something! Eating a larger volume of food in a day can obviously result in an increase in weight the following day. Also, eating later than usual can affect your weight the following day.
  • Food intolerances: Consuming foods that you are intolerant or sensitive to can result in inflammation of the digestive tract and subsequently cause bloating.
  • Hydration: Not drinking enough fluids can result in fluid retention. This is because the body stores water since it isn’t receiving enough, essentially entering a “survival mode”. Drinking more water will help to release more water.
  • Stress: This is a major factor in increasing water weight via the release of cortisol, the “stress hormone”. The abdomen is the main site of fluid retention from cortisol release. 
  • Sleep: This is similar to when the body is under stress. Not getting enough sleep means your body is not able to fully recover, resulting in cortisol release. 
  • Training: Lifting weights causes trauma to the muscle tissue. In order to rebuild the muscle fibres to make them stronger, your muscles retain water to speed up the process in the cells. Training can also cause stress on the body. 
  • Your period: Most women will retain water during their cycle due to fluctuating hormone levels. It’s normal to gain 1-3kg of fluid around the time of menstruation! Sometimes, it can be more accurate for women to compare weight from month-to-month perspective as a result. 
  • Alcohol: This is a diuretic which causes dehydration in the body, leading to water retention. This is a result of the body making up for the difference in water levels drinking alcohol causes. 

It is important to note that these are all temporary issues and that your weight will normalise within a few days. Know that these short term fluctuations have absolutely nothing to do with your long term progress.

To accurately track progress, our recommendation is to weigh yourself daily immediately after waking and going to the bathroom, before eating or drinking. We then take the average of these daily results across the week and measure that against the average of the previous week.

We know it’s easier said than done but try to remove the emotional connection to the scales and see them for what they are – a method for collecting data. It’s important to note that the scales only measure one thing – your total mass. They don’t measure the changes in your body composition (losing fat and building muscle). That’s why we also highly encourage you to take body circumference measurements and photos as well as weighing yourself these will help with showing you the bigger picture of your progress!

Like we tell our clients, focus on the things you CAN control: the food you consume, completing your training sessions and steps, and your mindset!

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Why your diet keeps failing & what to do about it
Why your diet keeps failing & how to set yourself up for success

In this FREE eBook, we go through some of the most common reasons why your diets keep failing and what you should do about it.