Weight loss of more than 5% (five percent) of body weight without an intention in less than one year time can be called unintentional weight loss and it can be a signal to a serious underlying pathology and underlying systemic disease. It is advisable for general physicians to investigate to find out the cause of weight loss of more than 5% in 6-12 months period. Weight loss should not be ignored if it is not intentional, as it may be due to serious medical problem and early diagnosis of the underlying disease can be managed better if diagnosed in time and as early as possible.

The causes of unintentional weight loss are many and in most of the cases of weight loss the cause can be found by careful physical examination and some direct investigations or testing. But in approximately 20%-25% of the cases of weight loss the cause can not be found despite extensive testing and in general their survival is much better than those individuals for whom the cause can be found.

The causes of weight loss are different in elderly and for the young adults. For the elderly the common causes of unintentional weight loss are depression, cancer and gastrointestinal pathology and for young adults the common causes of unintentional weight loss are diabetes, eating disorders and other psychiatric illnesses, hyperthyroidism and infections like HIV. The causes of unintentional weight loss are also different in males and females (in young adult females anorexia nervosa can be a leading cause of unintentional weight loss).

Causes of unintentional weight loss:
-- Atrophic Gastritis
-- Gastrointestinal disorders like malabsorption, pernicious anemia, obstruction of intestines etc.
-- Psychiatric disorders like depression, alcoholism, eating disorders (like anorexia nervosa), anxiety, etc.
-- Infections like HIV, tuberculosis, SABE (Subacute bacterial endocarditis), chronic worm infestations, etc.
-- Hormonal and metabolic causes like Hyperthyroidism, diabetes mellitus, adrenal insufficiency, etc.
-- Respiratory diseases like COPD (Chronic Obstructive Pulmonary Disease), Emphysema etc.
-- Cardiovascular diseases like chronic congestive heart failure, ischemia, Stroke etc.
 
Importance of Unintentional Weight Loss
Unintentional weight loss is important not only in looking for an underlying cause (3/4 of people who have unexpected weight loss have an underlying cause found by their doctors) but because of what it means in regards to health.  Unintentional weight loss is linked with higher morbidity (development of illnesses) a higher mortality (higher death rate) and a lower quality of life for people suffering from weight loss.  Cancer cachexia is a condition of unintentional weight loss combined with a few other concerns and is directly responsible for around 20 percent of cancer deaths.