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Unintentional weight loss

Weight loss is often a matter of choice - we choose to change our diet and exercise habits to become healthier. If there is a clear and healthy reason then weight loss is normal. Unintentional weight loss is different. This is when a person loses weight without trying. It is important to report it to a doctor so a cause can be identified. This leaflet lists some of the more common causes of unintentional weight loss.

At a glance

  • Unintentional weight loss is losing more than 5% of your body weight without trying.

  • Many health conditions can cause unintentional weight loss, including cancer and diabetes.

  • Mental health issues like anxiety and depression can also lead to unintentional weight loss.

  • Some other causes can include problems with food access or difficulty eating.

  • You should see a doctor if you keep losing weight for no reason.

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המשך לקרוא למטה

Some causes of unintentional weight loss

Weight loss is sometimes the first symptom noticed by the person, relative or friend. However, when carefully questioned by a medical professional, people may realise they have more symptoms in addition to their unintentional weight loss. Weight loss is usually defined as a loss of more than 5% of the person's body weight.

Common causes of unintentional weight loss are listed below. The list is not exhaustive.

סרטן

In the vast majority of cases of cancer, other symptoms will develop before any weight loss occurs. The first signs of cancer depend on the type and site of the cancer. However, occasionally, weight loss is the first symptom that is noticed. Common cancers that cause weight loss include those affecting the pancreas, the oesophagus, the stomach, the bowel ו the lung. The blood cancer lymphoma, of which there are several types, can cause unintentional weight loss among other symptoms.

סוכרת

Both Type 1 ו Type 2 diabetes can cause unintentional weight loss. As with all causes of unintentional weight loss, it is important to report this to your doctor, as early diagnosis is important.

הnxiety and depression

חרדה ו דיכאון have many symptoms and unintentional weight loss can occur for multiple different reasons. People suffering with these symptoms may experience weight loss or weight gain, for example, some people may respond by comfort eating, whilst others may experience a reduced appetite. Smokers may find they respond by smoking more; nicotine can reduce your appetite, causing weight loss. Some people may resort to alcohol to combat anxiety and this may also be associated with weight loss. Loneliness is a common experience for older adults and can affect a person's mood. Weight loss affecting someone whose mental health is suffering may be the most obvious symptom to family and friends.

Alcohol dependence

Some people who drink a lot of alcohol may struggle to look after themselves well, which can cause them to lose weight. Family and friends may show concern about weight loss and not be aware that the person has an alcohol problem.

Hyperthyroidism

Hyperthyroidism occurs when the thyroid gland produces too much of a hormone called thyroxine. This condition is also known as an overactive thyroid. The extra thyroxine causes many of your body's functions to speed up. This often causes many symptoms affecting different parts of the body. In the early stages of hyperthyroidism some people actually feel well and full of energy and don't realise they have a problem despite their weight loss.

Persistent (chronic) infection or inflammation

It would be unusual not to have other symptoms with a chronic infection. But, occasionally, the first symptom that is noticed with infections such as tuberculosis או HIV is weight loss. Hookworm infection of the gut is another example where weight loss may be the first indication of disease. Hookworm is a very common problem worldwide (but rare in the UK). Likewise, there are various conditions that cause persistent inflammation of a part or parts of the body. Again, other symptoms would be usual. However, sometimes an inflammatory condition such as polymyalgia rheumatica may make you feel vaguely unwell and lose weight prior to other symptoms developing.

Malabsorption syndromes

There are various diseases that can affect the way food is absorbed and taken into the body from the gut. These would normally cause gut symptoms such as diarrhoea and abdominal pain. However, weight loss may be the first symptom noticed. Examples include coeliac disease, מחלת קרוהן ו קוליטיס כיבית.

Dementia

People with דמנציה may struggle to look after themselves well and lose weight as a result. There can be many reasons for this. In older adults, weight loss may sometimes be the first symptom friends or family notice.

Eating disorders

In conditions such as anorexia, a person usually knows they are tightly controlling their diet and exercise and are actively trying to lose weight. However, this may be very carefully hidden from friends and family and may not be divulged even to the doctor.

Side-effects from medication

Sometimes medication may cause side-effects resulting in weight loss. For example, some medicines may cause a loss of appetite, or a פה. Some cause צרבת or give a mild tummy discomfort. Others may affect the sense of taste or smell, or make people feel sick. Any of these side-effects could affect eating habits and result in weight loss.

Other common causes

There are many reasons a person can lose weight unintentionally, and they are not all because of specific health conditions. Common issues such as lack of money, lack of access to food, difficulty buying and cooking food or difficulty eating can all cause unintentional weight loss. At each of these stages there are many, wide ranging causes which can result in unintentional weight loss. For example difficulty eating can be due to having a problem in your mouth or any condition affecting your ability to accurately place food in your mouth.

If you keep losing weight for no reason, see a doctor. This is because, as a general rule, the earlier a serious problem is diagnosed, the better the chance that treatment may improve the outlook (prognosis).

המשך לקרוא למטה

Your doctor is likely to ask various questions. He or she may actually uncover other symptoms that you were either unaware of or did not think were significant. He or she may also examine you. Tests, such as בדיקות דם, may or may not be appropriate. Following a doctor's assessment, the likely cause may be clear or you may require more investigations. Your doctor will advise on what is needed depending on what they think is causing the weight loss.

The treatment depends on the cause. See individual leaflets on the various diseases that can cause weight loss. The conditions above are not an exhaustive list.

שאלות נפוצות

What specifically is meant by 'unintentional weight loss'?

Unintentional weight loss is typically defined as losing more than 5% of your body weight without actively trying to do so. It is often noticed by the individual themselves, a relative, or a friend.

Can common mental health issues like anxiety and depression lead to significant weight loss?

Yes, both anxiety and depression can cause unintentional weight loss for various reasons. While some individuals might gain weight through comfort eating, others may experience a reduced appetite. Factors like increased smoking (nicotine reduces appetite) or alcohol consumption to cope with anxiety can also contribute to weight loss.

I'm an older adult and my family has noticed I'm losing weight, but I feel fine. Is this something to worry about?

For older adults, weight loss can sometimes be an early sign of conditions like dementia, where individuals may struggle to care for themselves adequately. Also, loneliness, which is common in older adults, can affect mood and lead to weight loss. Even if you feel well, unintentional weight loss in older adults can be a significant symptom.

How can medication side effects lead to losing weight?

Some medications can cause side effects that impact eating habits, leading to weight loss. These can include a loss of appetite, dry mouth, heartburn, mild stomach discomfort, changes in taste or smell, or feelings of nausea. Any of these can reduce how much you eat and result in weight loss.

Beyond medical conditions, what other everyday factors can cause unintentional weight loss?

Unintentional weight loss isn't always due to specific health conditions. Practical issues such as a lack of money, difficulty accessing food, challenges with buying or cooking meals, or problems with eating itself (like oral health issues or conditions affecting the ability to get food into your mouth) can all contribute to losing weight.

קריאה נוספת והפניות

  • חשד לסרטן: זיהוי והפניה; הנחיות NICE (2015 - עודכן לאחרונה באפריל 2026)
  • Cao Y, Hardy R, Wulaningsih W; Associations of medical conditions, lifestyle and unintentional weight loss in early old age: The 1946 British Birth Cohort. PLoS One. 2019 Apr 9;14(4):e0211952. doi: 10.1371/journal.pone.0211952. eCollection 2019.
  • CKS Malnutrition. February 2024 (UK Access only)

המשך לקרוא למטה

About the authorView full bio

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Dr Caroline Wiggins, MRCGP

General Practitioner, Medical Author

MBBS Honours (with Distinction), MRCGP (2016), MSc.SEM (with Distinction), BSc (Hons)

Dr Caroline Wiggins is a GP locum currently in the South-West of England. 

About the reviewerView full bio

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ד"ר טוני הייזל, MRCGP

MBBS, BSc, MRCGP, DFSRH, Dip GU med, DRCOG, DCH (London, UK, 2000)

Dr. Toni Hazell qualified from St. Mary’s Hospital Medical School and did her VTS at Northwick Park Hospital.

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