To remain fit and healthy is every individual's desire. In this quest, people undertake many measures like eating right, working out, playing a sport, etc. Losing weight due to regular exercise or following a healthy diet is normal, but losing weight without doing either, is a cause of concern. Sudden weight loss occurring in a short period of time can be an underlying symptom of various health issues―physical as well as mental―and should be brought to the notice of a doctor immediately.

Various health issues like Addison's disease, cancer, celiac disease, COPD (chronic obstructive pulmonary disease), Crohn's disease, dementia, depression, diabetes, eating disorders, HIV/AIDS, hypercalcemia, hyperthyroidism (overactive thyroid), narcotics, Parkinson's disease, peptic ulcer, ulcerative colitis etc., may cause unexpected weight loss.

This condition is also known as chronic adrenal insufficiency. This disorder occurs when hormones like aldosterone and cortisol are produced in insufficient quantities by the adrenal glands. This medical condition can be life-threatening if neglected. Sudden weight loss is one of the symptoms of Addison's disease.

Sudden loss of weight is a common symptom observed in individuals with cancer. This happens because the cancerous tumors present in the body increase the body's metabolism, due of which the body is able to burn calories faster, thus leading to excess weight loss. Some people may also experience an unexplained weight loss while undergoing treatment for cancer.

In this digestive condition, the lining of the small intestine gets damaged due to an adverse reaction to gluten. This condition is characterized by an inability to absorb certain nutrients. Weight loss occurs due to malabsorption of vital nutrients, followed by other complications that affect the liver, kidneys, peripheral nervous system and brain.

Diarrhea is caused when one consumes the wrong type of food or catches a viral infection called gastroenteritis. It is something that most people have experienced at some point in their life. Though such type of diarrhea can be treated with antibiotics, people who suffer from diarrhea for more than four weeks are said to have chronic diarrhea. When an individual has diarrhea for more than four weeks, weight loss is most likely to occur.

A group of lung diseases that block the airflow, leading to breathing difficult, are known as COPD (Chronic Obstructive Pulmonary Disease). This condition comprises emphysema (air sacks at the smallest air passages in the lungs are destroyed) and chronic bronchitis (the lining of the bronchial tubes are inflamed). In later stages of COPD, unintended weight loss is observed.

Crohn's disease is a rare disease that affects different areas of the digestive tract, causing inflammation of the tract lining. It leads to abdominal pain, severe diarrhea, and in some cases malnutrition. It is a painful and debilitating disease that may be life-threatening, if not diagnosed and treated on time.

Dementia is not really a disease, but is a group of symptoms relating to certain diseases like Alzheimer's, Parkinson's or Huntington's disease. It involves the loss of brain function, causing loss of memory, feeling confused, slurred speech, etc. Weight loss due to dementia is rare, but not unheard of. It persists in severe cases, when the patient has no memory if he/she has eaten food or not.

A mental condition that is characterized by the persistent feeling of sadness and loss of interest is known as depression. Among the various symptoms of depression, the most primary one is the weight loss due to lack of appetite, or even excessive weight gain due to overeating.

Diabetes is a disease characterized by elevated blood sugar level. Usually, if the sugar level goes higher than normal, the most common symptoms are excessive thirst, and unexplained weight loss. This is because, the excess sugar does not get absorbed by the kidneys, and as a result of which, it is passed in the urine. Every time sugar is passed in the urine, the diabetic feels thirsty, and tries to quench it with water, sodas, coffee, etc. This, in turn, makes the sugar levels rise and thus, the cycle goes on. This cycle is what causes the sudden weight loss in diabetics.

An eating disorder due to which people obsess about what they eat and how much they weigh, is called anorexia nervosa. Usually, people with anorexia nervosa, starve themselves, or indulge in excessive exercising. On the other hand, bulimia nervosa is when an individual restricts the intake of food, by vomiting after eating, consuming large amounts of laxatives or diuretics, and exercising excessively to lose weight.

Both these eating disorders should be treated quickly as these can turn life-threatening, especially anorexia, which is very common among teenage girls. People usually do this so that they can cope with emotional problems, as anorexia and bulimia are more mental conditions rather than physical ones.

A chronic and life-threatening condition caused due to HIV (human immunodeficiency virus) is known as AIDS (acquired immune deficiency syndrome). HIV interferes with the body's resistance towards diseases and infections by damaging the immune system. There are many other diseases which cause sudden loss of weight that accompany HIV or AIDS (as the immune system is already depleted, the body is like an open playground for various diseases), like tuberculosis (TB), salmonellosis, cytomegalovirus (CMV), candidiasis, toxoplasmosis, cryptosporidiosis, cancer, wasting syndrome, and kidney disease.

High calcium levels in the blood is known as hypercalcemia. Calcium is required for the maintaining bone density, contracting muscles, ensuring proper functioning of the brain and nerves, and also releasing hormones. When the parathyroid glands (glands that regulate blood calcium level) are overactive, it leads to hypercalcemia. This condition can go undetected, for years, if it is not in a very advanced stage, as the signs and symptoms are not severe. Although, in later stages, loss of appetite, excessive thirst, constipation, are some of the symptoms. Sudden loss of weight occurs in those who have hypercalcemia, due to the loss of appetite.

The excessive production of the hormone thyroxine, by the thyroid gland, is known as hyperthyroidism or overactive thyroid. Sudden weight loss, sweating, nervousness, irritability, and rapid or irregular heartbeat, are caused due to the acceleration of the body's metabolism because of hyperthyroidism.

Consuming narcotics like cocaine, heroine, amphetamines, etc., suppresses the appetite, causing weight loss. Stimulant and drug abusers often go on binges to soothe their cravings for drugs, wherein they avoid eating or sleeping for days at a time. This unhealthy lifestyle choice leads to various health problems and even possible death.

Parkinson's disease is a condition that affects the nervous system of the body, caused due to the dopamine-generating cells in the substantia nigra, a region of the midbrain. It is a degenerative disorder of the central nervous system, for which a cure has still not been found. Some of the symptoms of this medical condition are, stiffness in limbs, restriction in movement, slurred and soft speech, decreased ability to perform involuntary movements like blinking, smiling, swing the arms while walking, etc.; uncontrolled body movements like tremors and shaking of limbs, slowed movements, changes in handwriting, impaired posture and also balance problems. Sudden weight loss due to the uncontrolled tremors and loss of appetite is common with people who have Parkinson's disease.

Open sores that develop on the inner lining of the esophagus, stomach and upper portion of the small intestine are called peptic ulcers. They are caused due to prolonged consumption of certain medication or bacterial infection. The most common symptoms of peptic ulcers are vomiting blood (red- or black-colored), unexpected weight loss, appetite changes, and dark blood in stools.

Ulcerative colitis is a chronic condition that causes long-lasting inflammation in certain areas of the digestive tract. It is an inflammatory bowel disease which usually affects the innermost lining of the large intestine and rectum. The symptoms of this condition include, rectal bleeding, rectal pain, bloody diarrhea, abdominal cramps and pain, and an inability to move the bowels, in spite of the urge to do so, and unintended weight loss.

It is also fairly normal to experience weight loss after you recover from an illness, or stress of bereavement, changing jobs, or a divorce. However, if the unexpected weight loss was not due to any of these causes, then it should not be overlooked and should be reported to your medical healthcare professional immediately.

Disclaimer: This article is for informative purposes only, and should not be used as a replacement for professional medical advice.