Unexplained Weight Loss: What Symptoms Should You Alert?

Some dream of losing a few pounds without dieting or any deprivation. But involuntary and unexplained weight loss often signals a more or less serious health problem: depression, digestive or inflammatory diseases, or cancer… What are the warning signs? When to consult?

While some dream of losing a few pounds easily without dieting or deprivation, others struggle daily to gain weight. Indeed, we lose weight for no apparent reason: it can be the result of a simple fluctuation or a lifestyle change, but it can also be a sign of an underlying health problem. (especially if the weight loss is significant and/or persistent).

Is it normal to lose weight for no reason?

Any rapid and significant weight loss should be alert, especially if it occurs without lifestyle changes. Because? Rapid weight loss is normally the result of an imbalance between calorie intake (diet) and calorie expenditure (physical activity and basal metabolic rate). It may signal a health problem if you’re losing weight without intending to and without making any significant lifestyle changes, it may signal a health problem.

“Involuntary weight loss usually develops over a few weeks or months. It can be a sign of a major physical or mental disorder and is associated with an increased risk of death. Its cause can be obvious (chronic diarrhea due to a malabsorption syndrome, for example) or occult (undiagnosed cancer, for example, which tends to reduce appetite and increases caloric expenditure at the same time).

When to worry about weight loss?

Our weight changes throughout the day and is never fixed. It can also vary with seasons and life events. This is why doctors are sometimes relaxed about an increase or decrease in the pounds on the scale.

In general, the medical community considers weight loss clinically significant when a person loses more than 5% of their weight in less than six months or more than 10% in less than a year. However, this traditional definition does not distinguish between the loss of lean and fat body mass. The expert also notes that an accumulation of edema or tumor can compensate and mask worrying weight loss.

Fatigue, pain, loss of appetite… The associated symptoms that should alert

People experiencing unexplained weight loss often have these few associated symptoms:

  • Loss of appetite ;
  • Severe fatigue ;
  • Bone pain ;
  • Abdominal pain ;
  • Fever and night sweats ;
  • A change in the texture or color of the stool ;
  • Excessive thirst and a frequent urge to go to the toilet;
  • Shortness of breath, even a cough, sometimes accompanied by Bloody expectoration;
  • Etc

In older people, unexplained weight loss may also be accompanied by headaches, jaw pain when chewing, and /or blurred vision.

Causes: what diseases are likely to cause weight loss?

As noted above, weight loss is generally linked to people eating fewer calories than necessary. But many physical, emotional, and mental disorders can also cause unintentional weight loss. Overview (non-exhaustive).

An emotional shock or significant stress

The breakup, loss of a loved one, dismissal… After a major emotional shock, some people lose their appetite, leading to abnormal short-term weight loss.

In addition, excessive stress, which tends to promote weight gain through hormonal mechanisms, can also reduce appetite ( feeling in knots in the stomach ) and cause weight loss.


Loss of appetite and weight loss are hallmark symptoms of depression. If some people take refuge in food, others lose the taste and completely stop eating, so much the meals seem impossible to them.

Undiagnosed anorexia

Anorexia nervosa is now a well-known eating disorder (ED), which results in a refusal to maintain normal body weight (BMI often less than 18.4 kg/m²) and intentional weight loss. It mainly affects young women plagued by an erroneous perception of their bodies ( dysmorphophobia ). Therefore, weight loss is voluntary, but some patients do not notice it.

Chaotic disorders

Patients who have bipolardisorder can sometimes lose the feeling of hunger – or in any case, neglect it – in the specific medical condition or hypomanic phase. In fact, they lose weight without understanding the reason.

When not diagnosed or stabilized, patients with schizophrenia can also lose touch with reality and forget to eat or even refuse completely on the pretext that their food would be poisoned, for example.

Hormonal dysfunction (diabetes mal or hyperthyroidism)

A disorder of the thyroid gland can also have significant 

repercussions on weight. It promotes weight loss when it works in slow motion ( hypothyroidism ). But when it gets carried away (hyperthyroidism), the metabolism accelerates: the transit accelerates, the heart panics, our sweat production increases… Which can lead to weight loss for no apparent reason.

Undiagnosed or poorly controlled diabetes can manifest as weight loss and severe dehydration. The body’s inability to use glucose effectively causes it to tap into its fat and muscle stores.

A gastrointestinal disorder

Conditions such as celiac disease, Crohn’s disease, ulcerative colitis, or chronic pancreatitis can cause weight loss due to nutrient malabsorption, appetite disorder, or chronic inflammation.

An infectious disease (AIDS, tuberculosis, etc.)

Unexplained weight loss can also indicate a viral or bacterial infection such as tuberculosis, AIDS, hepatitis, pneumonia, etc. In question? Decreased appetite, increased energy requirements, and/or impaired metabolic function. The presence of an intestinal parasite, like the tapeworm, for example, can also drastically drop body weight.

An autoimmune disease

Several autoimmune diseases, such as rheumatoid arthritis, lupus, or multiple sclerosis, can cause weight loss due to systemic inflammation, pain, and fatigue which alters appetite and metabolism.


Certain medications, such as antidiabetics, amphetamines, and some antidepressants, can cause unintended weight loss that often goes unnoticed.

Drug use

Less well known, the consumption of drugs in large quantities, such as cannabis, cocaine, or certain opiates, also leads to a loss of appetite and noticeable weight loss.

In addition, significant consumption of alcohol can reduce energy needs and therefore be accompanied by weight loss!

A more or less advanced cancer

In some cases, unexplained weight loss can finally be an early symptom of certain cancers, such as lung, pancreatic, stomach, or lymphoma. In fact, cancer induces a decrease in appetite, impaired metabolism, and loss of body tissue.

Age and purchasing power

Finally, involuntary weight loss can also be linked to age: the older people, especially when isolated, can lose their appetite or refuse to eat and let themselves waste away (slipping syndrome). In addition, social and economic problems can also impact the regularity and quality of food intake – thus inducing involuntary weight loss.

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