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This month, we're diving deep into the relationship between our body weight and hormone health with Dr Rebecca Goadby MD FRACGP. From thyroid dysfunction to PCOS and perimenopause, we're unpacking the often overlooked medical causes behind weight gain — and cutting through the noise around treatment. For more, head to our Well hub here.

FACT SHEET: Weight and hormones.

Our body weight is determined by a complex set of factors including our genetics, hormonal function and lifestyle.

In medicine, noticeable changes to your weight over a short space of time (either weight loss or weight gain) is a symptom that requires discussion with your doctor. There are many causes for weight changes, and your doctor will explore these with you before referring to blood tests to investigate the cause.

The two most common underlying causes of weight gain in women who have had no change in lifestyle factors (e.g. diet, exercise, stress levels and sleep) are:

• Altered thyroid function

• Polycystic ovarian syndrome

• Perimenopause and menopause

In addition to assessing the above, your doctor will review any medication you are taking as weight gain can be a known side effect of some therapies.

There are also rarer causes that your doctor will consider, including adrenal gland disorders and pituitary gland dysfunction, as well as causes of fluid retention such as liver, kidney and heart disease.

And of course, if you are of child-bearing age, a pregnancy test is always a part of the work-up.

What is a 'normal' weight?

Our bodies are all unique and different, so there is no true 'normal' weight and health discussions should always be individualised for each patient.

However, modern medicine is evidence-based, and to gain this evidence, interpretation of data on a wider population level is needed. For this reason, there have been measures for weight introduced over the years which categorise our weight into various classifications. Whilst these classifications are useful in some situations, they should never be used in isolation when managing a patient's health and wellbeing.

The most widely known of these classifications is the body mass index (BMI) which uses height and weight to calculate results and classify people in a range from underweight to obese. This index was developed nearly 200 years ago to determine the 'average human size' and has been refined over the years, most recently by the World Health Organisation to classify clinical obesity. A BMI of 18.5 to 24.9 is classified as a healthy weight.

In recent years, BMI has been found to be less useful in the medical setting, with other measurements such as waist circumference and hip to waist ratio more widely used. You may find that your doctor will still measure your weight and height over time. Similar to keeping track of your heart rate and blood pressure, these numbers are useful in measuring overall health risks and determining preventative health measures for you.

Waist circumference and hip to waist ratio have been introduced due to evidence that central weight gain poses the greatest risk to our health. Higher levels of abdominal weight lead to an increased risk of heart disease, diabetes and certain cancers.

Listen: Well, co-hosts Claire Murphy and Dr Mariam explore the link between weight and PCOS. Post continues below.

What are treatment options for weight loss?

Weight loss counselling and management involves shared decision-making with your doctor and is a long-term strategy that will likely involve support from various clinicians.

Any weight-loss plan starts with education and support for lifestyle measures. This will include discussing the right meal and exercise plan for you, with referral to a dietitian or an exercise physiologist if needed. Medicare rebates may be available and many state and local governments also offer access to free or low-cost services to assist in these areas.

It is also important to ensure that you have a good quantity and quality of sleep, and that you have strategies in place for stress management. Developing a therapeutic relationship with a psychologist can help in these areas, and be beneficial to your ongoing health journey.

For those patients whose weight may be contributing to or creating a high risk of other health conditions (for example, diabetes, heart disease or arthritis), weight-loss surgery is an option.

This surgery results in a reduction of weight in line with treatment goals, with this weight loss being sustainable over a longer duration of time when compared to other treatment options. Unfortunately, surgery is expensive and invasive, so it may not be an option for all patients.

There are some Medicare rebates for medically indicated weight-loss surgery, and some private health insurers may assist with the cost. Some states may also have public hospital options available, so discuss with your doctor to explore this option further.

Watch: Nutritionist Lyndi Cohen explains how PCOS affects the body. Post continues below.

There has been a lot of noise around weight-loss medications in recent years. It is important to remember that these medications are currently only listed for use in patients who are at risk or who have health concerns related to their weight. And remember that all weight-loss medications are only effective with ongoing lifestyle modification, so it is important to incorporate these into any medication plan.

There are oral medications available as well as injectable medications, each with their own benefits and risks. Individual discussion with your doctor will determine if medication is the right option for you. This should include an informed discussion around cost, as currently none of these medications are listed on the Pharmaceutical Benefits Scheme (PBS) and can be expensive due to the long-term nature of their use.

Stay tuned for future editions of Mamamia's Well Fact Sheets, where we'll continue to bring you expert guidance on the health topics that matter most to women. For more, head to our Well hub here.

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Featured image: Getty.

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Well by Mamamia. Australian women, welcome to your full-body health check. At Well, our goal is to improve the health of one million Aussie women by delivering the game-changing health info they actually need. This initiative is made possible through the support of our presenting partner, Chemist Warehouse, and our body topic sponsors, Ostelin and MOVE.