Weight Loss and Loss of Appetite: What It Can Mean

When weight loss is a concern

Small fluctuations of 1 to 2 kg (2 to 4 lb) are normal. Doctors look for:

• 5% or more of body weight lost in 6 to 12 months without dieting
• weight loss with other symptoms such as fatigue, fever, pain, bowel changes or low mood
• older adults, in whom unintentional weight loss is linked to frailty and higher risk of illness

Weigh yourself on the same scale, at the same time of day, and note dates. Clothes becoming loose, or comments from others, are also useful clues.

Causes of weight loss with loss of appetite

Mental health

• Depression: one of the most common causes, especially in younger adults and older people. Doctors diagnose major depression when 5 of the following are present most days for 2 weeks: low mood, loss of interest or pleasure, significant weight or appetite change, insomnia or oversleeping, slowed or restless movements, fatigue, worthlessness or guilt, poor concentration, and thoughts of death.
• Anxiety and stress, bereavement and social isolation.
• Eating disorders: anorexia nervosa involves restriction and fear of weight gain, often with denial of illness.

Digestive diseases

• Peptic ulcers, gastritis and acid reflux that make eating painful
• Celiac disease and other malabsorption
• Crohn's disease and ulcerative colitis
• Chronic pancreatitis, liver disease and gallbladder disease
• Swallowing problems and dental problems

Cancer

Cancer causes weight loss through reduced appetite, altered metabolism and obstruction. Cancers of the stomach, pancreas, esophagus, lung, colon and blood (lymphoma) commonly present this way. Clues include age over 50, smoking, night sweats, a lump, persistent cough, difficulty swallowing, blood in stool or anemia.

Chronic infections

• Tuberculosis: cough, night sweats, fever
• HIV
• parasitic infections after travel
• long-lasting infections such as endocarditis

Long-term illness

Heart failure, chronic lung disease (COPD), kidney failure, rheumatoid arthritis and other inflammatory conditions cause appetite loss and muscle wasting (cachexia).

Medicines, alcohol and drugs

Many medicines reduce appetite or cause nausea or taste change: metformin, GLP-1 medicines (semaglutide, tirzepatide), some antidepressants, ADHD stimulants, digoxin, antibiotics, chemotherapy and opioids. Heavy alcohol use, smoking, cannabis withdrawal, cocaine and amphetamines also cause weight loss.

Older adults

Dementia, difficulty shopping or cooking, poor dentures, loneliness, reduced taste and smell, and multiple medicines all contribute.

Weight loss with loss of taste or smell

Loss of taste and smell makes food unappealing and leads to eating less. Common causes are viral infections (including COVID-19), chronic sinus disease and nasal polyps, smoking, zinc deficiency, some medicines, and aging. Less commonly it reflects neurological conditions such as Parkinson's disease or Alzheimer's disease. Persistent loss of taste and smell with weight loss should be assessed.

Causes of weight loss with a normal or increased appetite

How doctors investigate weight loss

A doctor will confirm the weight loss, then ask about appetite, diet, mood, bowel habits, swallowing, pain, fever, night sweats, cough, medicines, alcohol and drug use, and social circumstances. A full examination includes the mouth, thyroid, lymph nodes, chest, belly and, where relevant, breasts and rectum.

First-line tests usually include:

• full blood count, kidney and liver function, calcium, glucose and HbA1c
• thyroid function
• inflammatory markers (CRP, ESR)
• celiac antibodies
• urine test
• HIV and hepatitis tests where risk exists
• fecal immunochemical test (FIT) for hidden blood
• chest X-ray

Further tests depend on findings: endoscopy, colonoscopy, CT scans of the chest, abdomen and pelvis, or specialist referral. If the initial assessment and tests are normal, a period of careful monitoring is often recommended, as serious disease is less likely.

Treatment and support

• Treat the cause: antidepressants and therapy for depression, thyroid treatment, a gluten-free diet for celiac disease, antibiotics for infections, cancer treatment, adjusting medicines.
• Nutrition support: small, frequent, energy-dense meals and snacks; adding healthy fats such as olive oil, nut butters and full-fat dairy; nourishing drinks between meals.
• Dietitian referral for tailored plans and oral nutritional supplements.
• Practical help for older adults: meal delivery, help with shopping and cooking, dental care, eating with others.
• Appetite stimulants are occasionally used in specific situations such as cancer or advanced illness.

Frequently asked questions

What does loss of appetite and weight loss usually indicate?

It most often reflects depression, a digestive problem, a medicine side effect, an infection or another long-term illness. Cancer is a less common but important cause, especially in people over 50. Losing more than 5% of body weight in 6 to 12 months without trying should always be checked by a doctor.

What is the most common cause of weight loss due to lack of appetite?

In younger adults, depression and digestive conditions are among the most common causes. In older adults, cancer, gastrointestinal disease, depression and medicine side effects each account for a significant share. In about a quarter of cases, no cause is found after thorough testing.

How much weight loss is concerning?

Losing 5% or more of your body weight in 6 to 12 months without trying is considered significant. For someone weighing 70 kg (154 lb), that is about 3.5 kg (8 lb). Faster or larger losses, or weight loss with other symptoms, need prompt assessment.

Can depression cause weight loss and loss of appetite?

Yes. Depression commonly reduces appetite and interest in food, leading to weight loss, alongside low mood, poor sleep, fatigue and loss of interest. Some people eat more instead. Treating depression with therapy, medicine or both usually restores appetite.

What tests are done for unexplained weight loss?

Doctors usually start with blood tests (blood count, kidney, liver and thyroid function, glucose, calcium, inflammatory markers, celiac antibodies), a urine test, a stool test for hidden blood and a chest X-ray. Endoscopy, colonoscopy or CT scans follow if needed.