Reasons Why Your Weight Fluctuates

For those of us who weigh ourselves regularly, you might notice some unexpected ups and downs in your weight, despite having a consistent goal. Before you panic and adjust your diet, there are many factors to take into account which might have caused the change.



Fibre and Bloating

Fibre is an indigestible carbohydrate. While fibre is extremely important to have in your diet to keep you regular, a sudden increase in fibre can cause bloating. Many people find this when first transitioning to a plant based diet. Be mindful of which foods in particular cause you problems, vegetables like cauliflower are common IBS triggers.

Other indigestible carbohydrates include polyols, the artificial sweeteners found in gum and sugar free drinks. We often increase our consumption of both of these indigestible carbs when dieting to stay satiated.

Sodium and Water Retention


Sodium brings water into the cells. While it is important to have salt in your diet, especially as someone who trains to maintain electrolyte balance and prevent cramps, this can be an issue when eating out when food is often excessively seasoned. For example, you may have ordered a meal from a restaurant which fit your macros, but the salt content may cause you to weigh in a little heavier the next day. Continue to drink plenty of water and the water weight should drop off over the next day or two!

Another reason for water retention can be the female menstrual cycle. This can start five to seven days before your period and usually goes away by day three or four. While it is very individual, some women experience a fairly dramatic change in their weight over this time.

Finally, some medications may cause water retention.

Weighing or Eating at Different Times

Another factor which may cause a subtle difference in your weigh ins is timings. If you usually eat your last meal by 8pm, but are busy one evening and have to eat 2 meals 9-11pm, you may find your weight reflects this. The same can be said for having a longer/shorter sleep, changing the times since you last ate. Always weigh yourself fasted, without heavy clothes, on the same scales for the most accurate readings!

Not being as accurate as you think

If there are certain things which you don’t track in your diet, try to keep them consistent from day to day. Going from having no additions one day to having a cappuccino, 17 servings of low fat mayonnaise and 1kg of green vegetables the next day adds up. Be honest with yourself! The same can be said for making less effort with your cardio over time. Keep a number in mind of calories you want to burn or a level to have the machine on as a minimum and don’t let yourself start slacking.


What to do:

Weekly average weight. Take weigh ins every day, or as close to every day as you can, and calculate the average. This will make it much easier to see a trend in your weight changes and to assess when alterations need to be made.

Keep foods similar. While this is not necessary for day to day life, for a more intense goal, flexible dieting isn’t always the best option. Creating a meal plan from your macros helps to control variables so that it is easier to judge what is and isn’t working.

Though this is easier said than done, avoid letting the number on the scale dictate your mood. If you find this becoming a problem, put the scales away for a few weeks and rely on progress photos, measurements and how you feel in clothes.

About the Author

Savannah Westerby, BSc Sport and Exercise Nutrition. IG:@savannahwesterby
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