Unexplained or unintentional weight loss is a fall in body weight in a person who has not been dieting or exercising in order to lose weight.
Small changes in weight over time can be normal. Marked, continuing weight loss that the person cannot explain should nevertheless be investigated, particularly where other symptoms accompany it.
How much weight loss matters?
In general, losing about 5% or more of body weight unintentionally over 6–12 months is regarded as clinically significant.
For a person weighing 80 kg, for example, losing about 4 kg or more without making any effort to do so may require assessment.
It is not only the number of kilograms that is looked at, however. How quickly the weight loss has developed, the person’s age, their starting weight and the accompanying symptoms are also important.
What are the causes of unexplained weight loss?
Unintentional weight loss does not have a single cause.
The principal causes may include:
- Diseases of the digestive system
- Thyroid and other hormonal diseases
- Diabetes
- Chronic infections
- Certain cancers
- Chronic heart, lung or kidney disease
- Certain medicines being taken
- Conditions affecting appetite and nutrition
Assessment of unintentional weight loss is important in older people in particular.
Can diseases of the digestive system cause weight loss?
Yes.
Many diseases of the digestive system can cause weight loss.
Coeliac disease and malabsorption
Nutrients not being sufficiently absorbed from the bowel can lead to weight loss.
The weight loss may be accompanied by:
- Long-standing diarrhoea
- Bloating
- Anaemia
- Vitamin or mineral deficiencies
Crohn’s disease and ulcerative colitis
In inflammatory bowel disease, inflammation of the bowel, diarrhoea, abdominal pain, loss of appetite and a reduced food intake can all cause weight loss.
Chronic diseases of the pancreas
Where the pancreas cannot produce enough digestive enzymes, the digestion of nutrients — of fats in particular — can be impaired.
In this situation there may be:
- Weight loss
- Fatty or foul-smelling stools
- Diarrhoea
- Bloating
Diseases of the stomach and gullet
Difficulty swallowing, persistent nausea, vomiting, early satiety or marked discomfort after meals can leave a person unable to eat enough, and lead to weight loss.
Is weight loss a sign of cancer?
Unintentional weight loss can be seen in some cancers; not every unexplained weight loss means cancer, however.
Weight loss can be seen in certain cancers of the digestive system, including cancers of the stomach, pancreas, gullet and large bowel.
What matters is not attributing the weight loss to one particular disease on its own, but investigating its cause systematically.
Can thyroid disease cause weight loss?
Yes.
An overactive thyroid gland can speed up the metabolism and lead to weight loss even though the appetite is normal or even increased.
Symptoms such as palpitations, sweating, tremor of the hands, intolerance of heat or restlessness may accompany it.
Can diabetes cause weight loss?
Unintentional weight loss can be seen in uncontrolled or newly started diabetes.
Where the following are present together in particular:
- Drinking a great deal of water
- Passing urine frequently
- Weakness
- Losing weight despite an increased appetite
the blood sugar should be assessed.
Can there be weight loss without loss of appetite?
Yes.
In certain metabolic diseases, in uncontrolled diabetes, in an overactive thyroid, and in some conditions where nutrients are not sufficiently absorbed, weight loss can be seen even though the person’s appetite is preserved.
For this reason, “How is your appetite?” is an important clue in the assessment.
Which symptoms may matter alongside weight loss?
Assessment is particularly important if unexplained weight loss is accompanied by any of the following:
- Difficulty swallowing
- Long-standing abdominal pain
- Persistent nausea or vomiting
- Early satiety
- Long-standing diarrhoea
- Newly started and persisting constipation
- Blood in the stool
- Black stools
- Anaemia
- Jaundice
- Fever or night sweats
- Marked loss of appetite
- Persistent weakness
How is unexplained weight loss investigated?
The first stage of the investigation is a detailed history and physical examination.
The doctor assesses:
- How much weight has been lost,
- Over what period the weight loss occurred,
- Whether the appetite has changed,
- Eating habits,
- Bowel habit,
- The medicines being taken,
- The other symptoms accompanying it.
Depending on the patient’s circumstances:
- A full blood count
- Blood sugar
- Liver and kidney function tests
- Thyroid tests
- Markers of inflammation
- Coeliac tests
- Stool examinations
- Ultrasound
- Gastroscopy
- Colonoscopy
- Computed tomography or other imaging
may be required.
Not every patient needs all of these tests. The investigations are planned according to the person’s age, history, examination findings and accompanying symptoms.
When should a doctor be consulted?
If your weight is falling markedly and continuously although you are not trying to lose weight, it is appropriate to have this assessed.
Where the weight loss is rapid in particular, or where it is accompanied by symptoms such as bleeding, difficulty swallowing, persistent vomiting, jaundice, fever, marked weakness or severe pain, seeking help should not be delayed.
Remember
Unexplained weight loss is not a disease; it is a finding that needs to be investigated.
Not every unintentional weight loss means a serious disease. It may not be right, however, to put marked and continuing weight loss down to age, stress or loss of appetite alone.
The aim is not merely to regain the weight, but to establish what is causing the loss.
Sources
- Prof. Ali Tüzün İnce, MD