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Losing weight without trying: possible causes and when to see a GP

Guide Published

Losing weight without changing diet or exercise has many causes, from stress to thyroid or digestive conditions. The NHS advises seeing a GP as a precaution.

Key points

  • Unintentional weight loss means losing weight without changing diet or exercise, and the NHS says it is important to get it checked by a GP.
  • The NHS lists mental health conditions, digestive problems, overactive thyroid and heart failure among the causes.
  • A GP will ask about general health and may arrange tests or scans.

What is unintentional weight loss?

Unintentional weight loss is losing weight without changing your diet or exercise routine. NHS 111 Wales says unintentional weight loss can follow a stressful event and can sometimes signal a serious illness.

What can cause it?

Mental health conditions such as depression, anxiety, eating disorders and obsessive compulsive disorder (OCD) are on the NHS list. Digestive problems are listed, including coeliac disease and inflammatory bowel disease. Hormone conditions such as an overactive thyroid and type 1 diabetes can cause weight loss. Heart conditions such as heart failure are also listed. Some medicines can cause weight loss as well, and cancer is another possible cause.

When should you see a GP?

The NHS advises seeing a GP if you keep losing weight without changing your diet or exercise. NHS 111 Wales advises being seen promptly if the weight loss comes with other symptoms. NHS malnutrition advice also says to see a GP after losing a lot of weight unintentionally over a few months. A GP will ask about general health and may arrange some tests or scans.

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Educational content. This article summarises public guidance and announcements in plain English for education. It is not medical advice and it cannot say what is right for you: speak to a clinician about your own health, call NHS 111 if you are unsure what to do and 999 in an emergency.