In brief
Putting on weight, sometimes without an obvious reason. Weight around the waist carries extra health risk, and some conditions and medicines can cause weight gain.
- A build-up of fat around the waist is a sign of metabolic syndrome.
- Measure your waist halfway between your lowest rib and the top of your hip bone, after breathing out normally.
- Long-term sleep loss and continually shifting body clock rhythms can increase the risk of obesity, according to the NIH.
When to get help
Get help now
- If you are short of breath and cannot speak in full sentences, have chest pain, blue lips, or feel drowsy or confused, call triple zero (000).
See your doctor if
- Your weight gain is unexplained.
- It comes with tiredness, feeling cold, irregular periods or swelling.
Things that can contribute
- An underactive thyroid
- PCOS
- Cushing's syndrome
- Some medicines
- Long-term sleep loss
Questions you could ask your GP
- Should my thyroid or other hormones be checked?
- Could any of my medicines be causing weight gain?
- Would a dietitian or exercise physiologist help me?
Based on healthdirect Australia, Body mass index (BMI) and waist circumference. You can also check your symptoms with the healthdirect Symptom Checker, or speak with a registered nurse on 1800 022 222.
How it works
Unexplained weight gain is a symptom of an underactive thyroid, weight gain or difficulty losing weight is a symptom of PCOS, and weight gain around the torso is a sign of Cushing's syndrome. Some medicines, including some antidepressants, can cause weight gain.
A body mass index (BMI) of 25 to 29.9 is classed as overweight and 30 or more as obese, but BMI is less accurate for some people, including athletes and some ethnic groups. A waist of 80 cm or more for women, or 94 cm or more for men, means increased risk, and 88 cm or 102 cm means greatly increased risk.
Connections
4 connections on the map. Select a topic to read its page.
Unexplained weight gain is linked with
A build-up of fat around the waist is a sign of metabolic syndrome.
- Insulin resistance Supported
Having overweight, obesity or a large waist raises the risk of insulin resistance.
Unexplained weight gain can be caused by
Unexplained weight gain is a symptom of an underactive thyroid.
Source: healthdirect Australia, Hypothyroidism (underactive thyroid)
Weight gain or difficulty losing weight is a symptom of PCOS.
Source: healthdirect Australia, Polycystic ovarian syndrome (PCOS)
Medicines and supplements
General education only. Never start, stop or change a medicine without your prescriber.
Sources
- Body mass index (BMI) and waist circumference
- Hypothyroidism (underactive thyroid)
- Polycystic ovarian syndrome (PCOS)
- Cushing's syndrome
- Antidepressants
- Circadian rhythms
- Metabolic syndrome
Each connection above names its own source. See every source AskBioMap uses.
Summarised from healthdirect and the NIH. Sources read on 12, 13, 16 and 19 October 2026. General education only, not medical advice. Spotted a mistake? Please tell us through the HuBu-Intel contact page.