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Weight can change due to dietary habits, physical activity, or stress. However, if a person begins to lose weight rapidly without dieting or additional physical exertion, this may indicate health problems. It is especially important to pay attention to weight loss accompanied by a deterioration in well-being.

In this article, we will examine what degree of weight loss is considered significant, why it occurs, and which symptoms may indicate dangerous diseases. We will also explain when you should see a doctor and what examinations may be needed to determine the cause.

Sudden weight loss: how many kilograms is that?

Unintentional loss of more than 5% of initial body weight over 6–12 months is considered medically significant. For example, for a person weighing 60 kg, this is approximately 3 kg, and for a person weighing 100 kg — 5 kg. Therefore, weight loss should be assessed not only by the number of kilograms lost but also by their proportion relative to the initial weight and the rate of change.

For clarity, here are examples of how many kilograms correspond to a loss of 5% of body weight:

  • 50 kg — 2.5 kg;
  • 60 kg — 3 kg;
  • 70 kg — 3.5 kg;
  • 80 kg — 4 kg;
  • 90 kg — 4.5 kg;
  • 100 kg — 5 kg.

According to Cleveland Clinic, unintentional weight loss of more than 5% over 6–12 months is a reason to see a doctor. At the same time, rapid weight loss over several weeks or the appearance of additional symptoms requires attention even when less than 5% has been lost.

Doctors at Oxford Medical point out that body weight may fluctuate slightly throughout the day due to changes in the amount of fluid in the body, food intake, and bowel movements. To assess the actual trend, weigh yourself in the morning after using the toilet, before breakfast, on the same scales, and wearing the same clothes. Compare results over several weeks rather than individual daily measurements.

Why does a person suddenly lose weight?

Why does a person suddenly lose weight?

Sudden weight loss in men, just as in women, may have the following causes:

  • Inadequate nutrition. Reduced appetite, skipping meals, and difficulties with chewing or swallowing may lead to a calorie deficit and a gradual decrease in body weight.
  • Diabetes mellitus. When insulin is insufficient, the body cannot properly use glucose and begins to use up fat and muscle tissue reserves. Weight loss is particularly characteristic of newly diagnosed type 1 diabetes. Severe thirst, frequent urination, and weakness may also occur.
  • Hyperthyroidism. Excessive production of thyroid hormones accelerates metabolism, causing a person to lose weight even with a normal or increased appetite. Rapid heartbeat, sweating, trembling hands, and heat intolerance are often observed.
  • Digestive system diseases. Celiac disease, inflammatory bowel diseases, and pancreatic insufficiency may impair the absorption of nutrients. Weight loss is sometimes accompanied by diarrhea, abdominal pain, or changes in bowel movements.
  • Chronic infections. Tuberculosis, HIV infection, and certain other diseases may cause weight loss due to inflammation, reduced appetite, and increased energy expenditure. Accompanying symptoms depend on the specific infection.
  • Oncological diseases. Some malignant tumors cause decreased appetite, metabolic disturbances, and loss of muscle tissue. Weight loss may occur together with other symptoms or be one of the first noticeable manifestations.
  • Psychoemotional and mental disorders. Depression, anxiety disorders, and eating disorders may affect appetite, eating patterns, and body weight.
  • Taking medications. Some medications, particularly those used to treat diabetes and obesity, may reduce appetite or affect food absorption. If weight loss began after a change in treatment, it is necessary to inform your doctor.

Sudden weight loss in men may be associated with the same causes as in women. Sex alone does not make it possible to determine the origin of the symptom. It is more important to consider the rate of weight loss, changes in appetite, and the presence of other complaints.

Doctors at Oxford Medical recommend not attributing unintentional weight loss solely to stress or overwork if it continues. Even in the absence of other complaints, it is important to determine the cause of weight loss and undergo an examination if necessary.

Rapid weight loss: when is it dangerous?

Unintentional weight loss can be dangerous if the body loses not only fat reserves but also muscle tissue, water, and essential nutrients. This may lead to weakness, reduced physical endurance, and vitamin and mineral deficiencies. Rapid weight loss that is accompanied by a deterioration in well-being or occurs against the background of chronic diseases is of particular concern.

It is especially important to assess not only the number of kilograms lost but also how physical strength and the ability to perform everyday activities have changed. A person may experience rapid fatigue, notice a decrease in muscle mass, or become ill more frequently due to insufficient nutrient intake.

According to the recommendations of the National Institute for Health and Care Excellence, people with the following indicators require particular attention to their nutritional status:

  • unintentional loss of more than 10% of body weight over the past 3–6 months;
  • body mass index (BMI) below 18.5 kg/m²;
  • BMI below 20 kg/m² combined with a weight loss of more than 5% over 3–6 months.

These indicators suggest possible undernutrition and are grounds for considering the need for nutritional support. At the same time, nutrient deficiencies may occur even in people with normal or excess body weight.

Doctors at Oxford Medical recommend not attempting to compensate for significant weight loss solely by increasing the calorie content of the diet or taking dietary supplements. First, it is important to determine the cause of weight loss and assess the body's condition, since the approach to restoring weight depends on the underlying disease and the degree of depletion.

When should you see a doctor?

When should you see a doctor?

To determine the cause of weight loss, the first step is a consultation with a family doctor. It is especially important not to postpone an examination if:

  • body weight has decreased by more than 5% over 6–12 months without an obvious cause;
  • weight loss occurs rapidly or continues for several weeks;
  • persistent weakness, loss of appetite, or difficulty swallowing has appeared;
  • severe thirst, frequent urination, palpitations, or trembling hands have occurred;
  • prolonged diarrhea, abdominal pain, fever, or night sweats are observed.

Based on the results of the initial examination, the family doctor may develop a treatment plan or prescribe additional tests and refer the patient to a specialist, such as an endocrinologist or gastroenterologist.

Unintentional weight loss should not be ignored, even if it is not accompanied by other symptoms. Timely examination helps determine the cause of weight loss and, if necessary, begin treatment.

The information in this article is provided for informational purposes and is not intended as instructions for self-diagnosis or self-treatment. If symptoms of a disease appear, you should consult a doctor.

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