Reasons for Undesired Weight Loss

Weight loss that happens unexpectedly or causes a dramatic difference within a short period of time should be treated by a doctor. Sudden, undesired weight loss can indicate the presence of a serious illness, so it should be addressed as soon as possible. This is especially important for people who haven't made any major changes to their diets or activity levels and are still experiencing weight loss.

Cancer

• Weight loss and fatigue are the two most common (and usually some of the earliest) symptoms of cancer. This is due to a variety of reasons, including lack of appetite and an inability to absorb nutrients. People with cancer may also suffer from cachexia, a condition in which the body wastes away and gradually loses large amounts of muscle tissue and fat. This leads to weight loss and a sense of extreme fatigue. Weight loss is especially significant with certain cancers, such as lung, stomach and pancreatic cancers.

Stress and Depression

• While many people associate high levels of stress or clinical depression with weight gain, the truth is that many people have the opposite problem: they lose considerable amounts of weight when confronted with a difficult situation. Loss of appetite is a major factor, but since depression also affects activity level and the ability to concentrate and make decisions, people sometimes lose weight just because they're not interested in food or eating. Certain drugs used to treat depression, like dopamine reuptakers (particularly Effexor and Wellbutrin) cause patients to lose weight when taken regularly. Psychological issues, including eating disorders, can also lead to weight loss, even if the person does not consciously strive for it.

Gastroenteritis

• Gastroenteritis is the inflammation of the intestines as a result of infection, either viral or from parasites. This leads to malabsorption, but also causes nausea, vomiting and diarrhea, all of which affect the amount and quality of the food consumed. In most cases, gastroenteritis does not need any particular treatment and goes away on its own, although it may sometimes trigger a more serious condition known as irritable bowel syndrome. Gastroenteritis causes dehydration and weight loss in almost all cases.

Geriatric Weight Loss

• Elderly people may lose weight as a result of disease, difficulty chewing or simply because of their age. As the body gets older, loss of muscle mass is inevitable, as are teeth problems and depression, all of which may result in undesired weight loss. The elderly also have fewer energy requirements, so their metabolism slows down and their appetite decreases. Dramatic weight loss over a very short period of time may indicate the presence of serious disease.

Thyroid Disorders

• An overactive thyroid (hyperthyroidism) can result in significant weight loss, along with rapid heart beat, fatigue and increased nervousness. Diagnosis is easy and takes just a blood test (which determines a high level of T4), although symptoms are sometimes confused with those of other illnesses, including cancer or heart problems, in which case diagnosis is sometimes delayed. Medications and radioactive iodine are used to treat hyperthyroidism, but relapses happen in up to 80% of patients. There is also a chance that patients will develop hypothyroidism (underactive thyroid) as a result of treatment, which may result in weight gain, heavy menstrual cycles and slowed thinking.