Unexplained Weight Loss: When It Might Signal a Health Problem

By Sarah MooreReviewed by Danielle Ellis, B.Sc.

Common causes of weight loss
Defining unexplained weight loss
Potential serious health issues indicated by unexplained weight loss
Diagnostic approaches
Case study
When to seek medical advice
Conclusion 
References

There are many reasons why a person may lose weight. Weight loss is often related to changes in diet and lifestyle, such as making healthy food choices, engaging in physical activity, or switching driving for walking.

Health issues can also cause weight loss. Stomach flu can cause weight loss due to vomiting, diarrhea, and the inability to intake food and fluids. Chronic stress and anxiety can also lead to changes in weight (both increases and decreases).

Unexplained weight loss can sometimes be a symptom of a more serious health condition. Unexplained weight loss can be a symptom of diabetes, gastrointestinal disorders, some types of cancer, and even some mental health disorders such as depression.^1-3

In this article, we explore the potential underlying causes of unexplained weight loss, highlighting the importance of recognizing when it may be a red flag for a serious health issue.

Common causes of weight loss

Changes to diet and physical activity are common benign causes of weight loss. Stress is another major factor in weight change (both weight loss and weight gain). Weight loss attributed to these causes can often be managed with lifestyle adjustments.

Sometimes, the cause of weight loss can be more serious. Chronic illnesses such as those outlined above can underlie weight loss, particularly when it is unexpected. It is important to recognize the cause of weight loss, as sometimes weight loss can be a symptom of an underlying illness that requires medical attention.

Defining unexplained weight loss

Unexplained weight loss is defined as the loss of more than 5% of body weight during a 6-12 month period without trying or without knowing the reason.⁴

Paying attention to weight loss, particularly when it is unintentional, is important as it can indicate an underlying medical issue. Unintentional weight loss might be a symptom of a health issue that needs to be addressed.

Potential serious health issues indicated by unexplained weight loss

While weight loss is often the result of intentional lifestyle changes, sometimes it can be the symptom of a serious health condition.

Endocrine disorders, such as diabetes and hyperthyroidism, can lead to weight loss due to metabolic imbalances. Diseases that affect the liver, which is responsible for nutrient processing, and the kidney, which governs waste elimination, can also cause unintended weight loss.^5,6 Gastrointestinal disorders, including Crohn’s disease, can cause weight loss due to issues with nutrient absorption.

Some cancers can cause unintentional weight loss, such as esophagus, lung, pancreas, and stomach cancer. These types of cancer can disrupt normal appetite and digestion due to their impact on the metabolism.

Other health issues that can also result in weight loss include chronic infections, such as tuberculosis, cardiac diseases, and mental health illnesses, such as depression.

Diagnostic approaches

When a person notices they have lost weight unintentionally, the first step is usually to consult with a primary care physician, who will begin the diagnostic process. A physician will often consider the person’s medical history and perform a physical examination. They might conduct basic tests such as blood tests and urine tests, and they may also run imaging tests (such as ultrasounds or x-rays) if they are deemed necessary.

These initial tests are used to identify potential causes when none is apparent. If a test or part of someone’s medical history suggests a potential cause, the person will likely be referred to a healthcare professional who specializes in that area.

Early diagnosis is important as it allows early treatment of the condition, which can often result in improved outcomes and fewer complications.

Case study

Unexplained weight loss can be the initial symptom of a serious health issue, and if dismissed or attributed to the wrong cause, the health issue can go untreated. BMJ case reported presented the case of an 80-year-old lady who had a history of weight loss and malnutrition.⁷ Her weight loss was initially attributed to her medical comorbidities. However, after being admitted to the hospital, it became clear that her weight loss was caused by depression and the eating disorder she had subsequently developed.

It is important to understand the root cause of weight loss so that its cause can be properly addressed.

When to seek medical advice

There is no rule on when specifically to seek medical advice. If a person has experienced weight loss that they cannot explain or did not expect, seeking the advice of a healthcare professional is generally a good idea. Particularly, if a person loses 5% or more of their body weight within a short period of less than a year, it is important to check the reason behind the weight loss. Even if it seems that the weight loss may be due to a medical comorbidity, a healthcare professional can check that this is the true reason.

Conclusion

Overall, it is important to recognize unexplained weight loss as it can potentially be an indicator of an underlying health condition. Bringing unexplained weight loss to the attention of a healthcare professional is important in ensuring that any potential underlying health condition is not left untreated.

References

1. Fromhold-Treu, S. and Lamprecht, G. (2016) ‘Gastrointestinale Ursachen von Gewichtsverlust: Klinik, Diagnostik, therapie’, DMW - Deutsche Medizinische Wochenschrift, 141(04), pp. 253–260. doi:10.1055/s-0041-111200.
2. Nicholson, B.D. et al. (2018) ‘Weight loss as a predictor of cancer in primary care: A systematic review and meta-analysis’, British Journal of General Practice, 68(670). doi:10.3399/bjgp18x695801.
3. Unexplained Weight Loss [online]. Diabetes UK. Available at: https://www.diabetes.co.uk/symptoms/unexplained-weight-loss.html
4. Weight-loss - unintentional [online]. Medline Plus. Available at: https://medlineplus.gov/ency/article/003107.html
5. Mak, R.H. et al. (2011) ‘Wasting in chronic kidney disease’, Journal of Cachexia, Sarcopenia and Muscle, 2(1), pp. 9–25. doi:10.1007/s13539-011-0019-5.
6. Tsai, J.-H. et al. (2017) ‘Aggressive non-alcoholic steatohepatitis following rapid weight loss and/or malnutrition’, Modern Pathology, 30(6), pp. 834–842. doi:10.1038/modpathol.2017.13.
7. Taylor, I.A., Gill, I. and Harripaul, A. (2015) ‘Unexplained weight loss in an 80-year-old woman’, BMJ Case Reports[Preprint]. doi:10.1136/bcr-2014-206847.

Further Reading

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• Mental Health Disorders, Weight Gain, and Exercise
• Circadian Rhythm and Weight Loss
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