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It is common to experience weight fluctuations throughout the course of a day, which can often add as much as 1-2kg to the scales! Most of us weigh less in the morning, after we void, and often weigh the most in the evening after dinner. Such temporary fluctuations can be due to an array of factors such as dietary intake and digestion, fluid retention, stress, sleep deprivation, physical activity and medications.

Dietary Intake & Digestion 

Regardless of the caloric content, all foods and beverages weigh something.

Naturally, following a meal our weight will increase based on the weight of the meal itself (for example if your dinner weighs 500g then chances are this will also add 500g to your scales if you were to weigh yourself immediately afterwards). Foods particularly rich in carbohydrates and sodium will cause your body to retain more water. Carbohydrates are stored in the body in the form of glycogen and the more glycogen your body stores the more water your body will retain. For every one gram of carbohydrate stored in the body (as glycogen) there are approximately two grams of water retained. A similar effect is seen with excessive sodium (salt) intake due to a process known as ‘osmosis’ which results in water retention within our cells.

Following this, the digestive and metabolic processes that occur after food consumption can also influence the number on the scales. Fibre-rich foods such as whole grains, fruits, vegetables, beans and legumes are digested by bacteria within our gut resulting in gas production. This is a natural process that occurs during digestion which can leave you feeling bloated and “puffy”. In saying this, these foods should not be avoided as they are essential for a healthy well-balanced diet.

Fluid Retention

Fluid retention, also known as “water weight”, is the build-up of water in the body commonly around the regions of the abdomen, arms and legs. This is a natural process that occurs due to a range of factors such as hormonal imbalances, menstruation cycle in women, reduction in exercise and physical activity, medication, increased sodium (salt) intake.  Fluid retention can increase an individual’s weight on the scales by 1-2 kg! To reduce fluid retention and water weight, you should aim to consume 2-3L of water per day, reduce your salt intake to no more than one teaspoon a day (or 2,000 mg of sodium a day) and insure you keep active.


How often do we race back home and raid the fridge after a bad day at work? Does eating a tub of ice-cream or a bar of chocolate seem to be the only thing that makes you feel better about life stressors? You are not alone, we all experience this and the science behind this is based on our hormonal responses to stress. When life’s demands get too intense, our body increases the secretion of cortisol which is known as the the “stress hormone”. This leads to increased fluid retention as well as an increase in our appetite and desire for foods high in sugar and fat (aka comfort foods).

Sleep Deprivation

Studies reveal that a lack of sleep or poor quality of sleep can result in an increase in both cortisol and ghrelin hormones leading to an increase in hunger and appetite.

We encourage you to aim for a full 8 hours of sleep per night and try to reduce your screen time prior to bedtime to improve your quality of sleep.

Physical Activity

Resistance training and endurance exercises can cause micro-tears within our muscle fibres. As our body begins to repair these tears, this results in fluid retention around the inflicted muscle areas. Fluid retention as a response to strenuous muscular contractions may take up to 72 hours to subside.  Additionally, if you have been working out more regularly or intensely, chances are you have also gained muscle mass resulting in an increase in the number on the scales.


Numerous medications can promote weight gain and can lead to weight fluctuations due to fluid retention, increased appetite and the temporary alteration in where the body stores fat. These include anti-inflammatory steroid medications such as prednisone, antipsychotic drugs (used to treat disorders like schizophrenia and bipolar disorder), alongside medications to treat migraines, seizures, high blood pressure, allergies and diabetes.

Contrary to popular belief, birth control pills containing estrogen and progestin have not been proven to causing lasting weight gain. Some women may experience weight gain in the early stages, however this is usually not a drastic increase and is often only short term.

Dietary interventions and regular physical activity can be effective in controlling weight whilst on medication however results occur progressively over a longer period of time.

By no means do we encourage you to cease your medication to improve your weight outcomes. If you are concerned about possible weight gain we encourage you to seek your GP first.

Medical Conditions

It’s important to note that various medical conditions can cause regular fluctuations in weight, due to hormonal imbalances, decreased metabolism, fluid retention or secondary to medication use and therapy. Most commonly, conditions such as Polycystic ovary syndrome and hypothyroidism.

In summary, an array of factors will cause a shift in the number on the scales which is not necessarily reflective of fat gain. For these very reasons we encourage you to avoid weighing yourself daily but instead limit this to weekly. Instead, shift your focus to the factors that you can control and less on the ones you can’t. Don’t get too caught up on the numbers and work hard on looking after your health and nutrition. Whether that’s improving your sleep routine, upping your daily water intake and being more mindful of your food choices.

By Annalise Farah, Accredited Practicing Dietitian (APD) – BMedSc & MND