Why does my weight fluctuate?

By Christina Ross, Accredited Practising Dietitian (APD)

Ever notice your weight fluctuate day to day even when following a structured diet and exercise routine? Your weight loss efforts seem to be paying off and then suddenly the scales say you’ve gained 500g or even 1kg overnight? Watching your weight go up and down each day can be very frustrating especially when you are trying to lose weight, but it’s important not to be disheartened by these slight changes on the scales as weight fluctuations are normal and are not commonly a reflection of changes in fat mass.

There are several reasons why weight fluctuates temporarily, all of which are mainly due to changes in body water.

  1. A greater intake of salt in your diet – Consuming processed and take-away food or adding more salt to cooking can result in water retention.
  2. Increasing your intake of carbohydrates – When you consume more carbohydrates than your body requires, they are stored in the liver and muscles in a form known as glycogen. When 1 gram of carbohydrate is stored, so is 3 grams of water which can cause the scales to temporarily shift upwards. However, if you continue to consume more calories than your body needs, this can in fact result in true weight gain.
  3. Hormonal changes – Menopause or menstruation is known to cause water retention due to fluctuating hormone levels.
  4. Constipation – Extra ‘weight’ may appear on the scales if you are not regularly opening your bowels.
  5. A reaction to hot weather – In hot weather, fluid-conserving hormones are released to signal the kidneys to retain more fluid (to prevent dehydration).
  6. Weighing yourself at different times of day – This can cause variation in your weight as we are all naturally heavier towards the second half of the day due to the fluid and food we’ve consumed.

Considering one or all the above scenarios can influence your weight at any given time, it’s important to not let these weight fluctuations deter you from jumping on the scales each day – a habit that’s been shown to support your weight loss efforts. The overall trend of weight loss is what matters most, so focus on the bigger picture.

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