Unexplained weight loss

Overview

Unexplained weight loss is when you lose weight without trying and do not know why. It usually means losing a significant amount of weight (for example, more than 5% of your body weight) over 6 to 12 months. This is not weight loss from dieting or exercise. It can be a sign that something in your body is not working correctly.

Unexplained weight loss is less common than intentional weight loss, but it does happen. It is more common in older adults and people with chronic health conditions.

Unexplained weight loss can affect anyone, but it is more common in people over 60, those with chronic illnesses like diabetes or thyroid problems, and people who have an infection or cancer.

Symptoms

Common symptoms

• Losing weight without trying, especially more than 5% of your body weight in 6 to 12 months.
• Loss of appetite or feeling full quickly after eating.
• Feeling very tired or weak.
• Fever or night sweats.
• Changes in bowel habits, such as diarrhea or constipation.

Symptoms in children

• Poor growth or not gaining weight as expected.
• Lack of energy or being less active than usual.
• Irritability or changes in mood.
• Frequent infections or illnesses.

Symptoms in older adults

• Weight loss over several months without trying.
• Loss of muscle strength or feeling frail.
• Difficulty swallowing or changes in taste.
• Memory problems or confusion.

Causes

Main causes

• Uncontrolled diabetes (type 1 or type 2).
• Overactive thyroid (hyperthyroidism) – the thyroid gland makes too much hormone.
• Infections such as tuberculosis, HIV, or chronic infections.
• Digestive disorders like Crohn’s disease, ulcerative colitis, or celiac disease.
• Cancer – weight loss can be an early sign of some cancers.
• Depression or anxiety – mental health problems can affect appetite and eating habits.
• Side effects of medications.
• Chronic lung disease, kidney disease, or heart failure.

Risk factors

• Being over 60 years old.
• Having a chronic illness like diabetes, thyroid disease, or cancer.
• Smoking or heavy alcohol use.
• Living alone or having limited access to food.
• Taking multiple medications that may affect appetite or absorption.

When to see a doctor

See a doctor urgently if:

• If you have lost a lot of weight quickly (more than 5% in less than 6 months) and feel very unwell.
• If you have severe symptoms like high fever, severe pain, or confusion.

Book a routine appointment if:

• If you notice you are losing weight without trying, even if it is gradual.
• If you have other symptoms like fatigue, changes in appetite, or bowel problems.

Diagnosis

Your doctor will ask about your medical history, symptoms, and eating habits. They will do a physical exam and may order tests to find the cause.

Tests that may be done

• Blood tests – to check for diabetes, thyroid problems, infections, or inflammation.
• Urine tests – to look for signs of infection or kidney problems.
• Imaging tests like X-rays, CT scan, or ultrasound – to look for tumors or other issues.
• Stool tests – if you have digestive symptoms.
• Other tests depending on your symptoms, such as a biopsy (taking a small tissue sample) if cancer is suspected.

What to expect at your appointment

Your doctor may refer you to a specialist, such as a gastroenterologist (digestive health) or an endocrinologist (hormones). They will work with you to find the cause and start treatment. The process may take a few weeks, but it is important to be patient and follow your doctor's advice.

Treatment

Treatment for unexplained weight loss focuses on the underlying cause. Once your doctor knows what is causing the weight loss, they will recommend a plan to address it.

Self-care at home

• Eat small, frequent meals throughout the day to increase calorie intake.
• Choose nutrient-dense foods like whole grains, lean proteins, fruits, and vegetables.
• Add healthy fats like olive oil, nuts, or avocado to meals.
• Drink plenty of fluids, but avoid filling up on water before meals.
• Keep a food diary to track what you eat and any symptoms.

Medical treatments

Depending on the cause, treatment may include medications to control blood sugar, thyroid hormone, or infections. You may also receive nutritional support, such as supplements or feeding tubes if needed. Your doctor will tailor the treatment to your specific condition. Always take medicines exactly as prescribed and discuss any side effects with your healthcare provider.

When is surgery considered?

Surgery is not used to treat the weight loss itself, but it may be needed to treat an underlying condition that causes weight loss, such as a tumor or a digestive blockage. Your doctor will explain if surgery is an option for you.

Living with this condition

Managing unexplained weight loss involves addressing the cause and supporting your body. Weigh yourself regularly, but do not obsess over numbers. Focus on how you feel and your energy levels.

Lifestyle tips

• Eat small, frequent meals with protein and healthy fats.
• Stay active with light exercise like walking or stretching, as tolerated.
• Manage stress through relaxation techniques like deep breathing or meditation.
• Get enough sleep to help your body recover.
• Quit smoking and limit alcohol.

Diet and exercise

Eat a balanced diet with enough calories to maintain a healthy weight. If you have trouble eating, try smoothies or soups. Gentle exercise can help maintain muscle mass and improve appetite, but listen to your body and rest when needed.

Mental health and emotional wellbeing

Unexplained weight loss can cause anxiety, stress, or sadness. It is normal to feel worried. Talk to your doctor or a mental health professional if you feel overwhelmed. Remember, you are not alone – support is available.

Prevention

Not all causes of unexplained weight loss can be prevented, but you can reduce your risk by maintaining a healthy lifestyle, managing chronic conditions, and seeing your doctor for regular check-ups.

Screening programmes

Regular health screenings for conditions like diabetes, thyroid disease, and certain cancers can help detect problems early. Ask your doctor which screenings are right for you based on your age and health history.

Complications

If left untreated

• Malnutrition – not getting enough nutrients.
• Weakened immune system – making you more prone to infections.
• Loss of muscle mass and strength (sarcopenia).
• Fatigue and decreased ability to do daily activities.
• Worsening of the underlying disease.

Long-term outlook

The outlook depends on the cause. Many conditions that lead to unexplained weight loss are treatable, and with proper medical care, most people can regain weight and feel better. Early diagnosis gives you the best chance for recovery.

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