5 possible reasons for unexplained weight loss

Written by: Dr Aathavan Loganayagam
Edited by: Laura Burgess

If you are losing weight unintentionally, it may be the sign of an underlying health problem. It is normal for your weight to fluctuate and even during the day the average adult’s weight can temporarily increase by an extra three to six pounds as you eat and drink.

It is common to gain weight during the winter when you are less likely to be active as opposed to in summer when you may be motivated to workout and may also find it too hot to eat anything heavy. There are, of course, limits to what is understood as normal weight fluctuation. In a world where most of us are worried about weight gain, it can be difficult to determine when we should worry about weight loss.

Generally, if you lose five per cent of your body weight in a six-month period and you can’t pinpoint a reason for the loss (change of diet, increased physical activity or stomach bug), it can be an early warning sign of a serious health problem. Here, one of our expert gastroenterologists Dr Aathavan Loganayagam explains what these possible illnesses may be.

Woman yawning as she gets out of bed.

What are the commonest causes of unexplained weight loss?

Here are five common conditions that can cause unexplained weight loss:

  1. Diabetes
    Diabetes is a metabolic disorder in which you may have high blood glucose levels (blood sugar) either because sufficient insulin is not produced in your body or because your body does not respond properly to insulin or even both. You might also be making more frequent trips to the toilet and finding yourself increasingly thirsty. Diabetes can cause your body to suck nourishment from your muscles, fuelling your weight loss.
  2. Thyroid issues
    Weight loss is a common symptom of an overactive thyroid (hyperthyroidism) and can be accompanied by increased hunger, heart palpitations, sleeping problems and feeling hot all the time. Around one in 20 people will experience some form of thyroid dysfunction in their lifetime. The most common cause is Graves' disease, which is due to an immune system abnormality. Other causes of an overactive thyroid include local inflammation (thyroiditis), nodules or lumps. There is no cure for hyperthyroidism, but it can be successfully managed with treatments such as anti-thyroid medication.
  3. Cancer
    Cancer is often the first thing people think of when they suffer any unexplained weight loss. While it is true that weight loss can be an early warning sign for many different types of cancer, you should look for other symptoms before jumping to conclusions. Symptoms to pay attention to include: severe pain that is getting worse, lumps or thickening under the skin, sores or ulcers that don’t heal, coughs that won’t go away, swallowing problems or persistent indigestion/vomiting, changes in bowel or bladder habits or blood in your stool.
  4. Depression
    Depression is a mood disorder in which feelings of sadness, loss, anger or frustration interfere with everyday life for weeks or longer. Older people with depression tend to present with unexplained weight loss as a symptom more frequently than younger people do. An older person is more likely to present to their GP with various physical complaints and difficulty sleeping rather than complaints of sadness or low mood. 
  5. Polymyalgia rheumatica
    Polymyalgia rheumatica is a condition causing pain and stiffness in older adults. As well as unexplained weight loss, other typical symptoms include moderate-to-severe muscle pain and stiffness, particularly affecting the neck, shoulders and thighs. The onset is usually sudden. People aged 50 years and over are most affected by polymyalgia rheumatica, and it becomes more common as people get older. The condition can be easily treated with corticosteroids, pain-relieving medications, and non-steroidal anti-inflammatory drugs.

If you have been experiencing unexplained weight loss over the course of a few months, please visit your GP immediately. You can also book an appointment with Dr Loganayagam via his Top Doctor’s profile here if you need to see a specialist for further investigations.

By Dr Aathavan Loganayagam

Dr Aathavan Loganayagam trained in medicine at Guy’s, King's and St. Thomas’ medical schools. He then underwent rigorous structured specialty training in gastroenterology and general internal medicine in the well respected South London training programme.

He then spent two years during postgraduate training as a research and endoscopy fellow at Guy’s and St Thomas’ Hospitals, London. His research was in the fields of pharmacogenetics, inflammatory bowel disease and gastrointestinal malignancy. He has received awards and grants for outstanding research work, including the prestigious NHS Innovation London Award.

Dr Loganayagam has numerous publications in peer reviewed journals on all aspects of gastroenterology. He is actively involved in clinical research. He has particular local expertise in the practice of personalised medicine and the utilisation of novel therapeutic agents in the treatment of complex inflammatory bowel disease. He is currently the lead clinician for endoscopy at Queen Elizabeth Hospital, Woolwich.

Diagnostic and advanced therapeutic endoscopy remains a major part of his clinical expertise, including assessment and treatment of inflammatory bowel disease, strictures, polyps and cancers.

Dr Loganayagam is an approachable doctor who takes pride in his communication skills with patients. He is keen to ensure that patients are fully informed and involved in all aspects of their care.

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