Unexplained Weight Loss

Although some degree of fluctuation in weight is normal, significant or persistent weight loss can signal the presence of underlying factors affecting your overall health. According to the Mayo Clinic, weight loss within six to 12 months amounting to 10-plus pounds or more than 5 percent of your body weight merits a further investigation into its causes.

Diet And Exercise Level

The average person may burn anywhere between 1,500 and 3,000 calories per day. This means that changes in caloric intake or activity level could be a primary factor in unexplained weight loss. Exercise can increase daily expenditures by 400 calories or more, while adopting a low-fat, low-sugar diet can reduce calorie intake dramatically.

Medication Use

Some over-the-counter and prescription medications may cause weight loss, such as antidepressants or birth control pills. If you are taking medication regularly, you should read the package carefully to determine its side effects and seek advice from your doctor if your situation continues to worsen.

Hyperthyroidism

Hyperthyroidism is a condition referring to an overactive thyroid gland, which produces excess amounts of the hormones thyroxine, triiodthyronine or both. Because the thyroid gland is important in regulating your metabolic rate, the speed at which your body expends energy, a change in its condition can cause rapid and persistent weight loss. Hyperthyroidism can be diagnosed by your doctor through physical examination and blood testing.

Infection

Chronic infections, such as tuberculosis or an AIDS-related illness, can cause weight reduction through the loss of bodily fluids--such as through vomiting. In addition, intestinal infections such as Giardiasis, which is a microscopic parasite which causes diarrhea, can also cause weight loss. Giardiasis can be found in contaminated water sources, such as lakes, rivers and streams. Drinking treated water and thoroughly washing all fruits and vegetables can significantly lower your risk of contracting intestinal parasites.

Cancer and Digestive Diseases

According to a Discovery Health article on unexplained weight loss, colon cancer, lung cancer, leukemia and others can be a cause of weight loss due to its ability to affect the way nutrients are absorbed into the body through the intestines. The body may also expend more energy, devoting to combating these long-term illnesses, which could cause weight loss if food consumption was not increased accordingly.

Mental Health

Although the link between mental health and body weight is not well understood, depression, anxiety disorder, anorexia, and bulimia have been linked to weight loss due to the way they affect the diet choices of those who suffer from these conditions. If you feel that your mental health may be affecting your eating habits, efforts to reduce the stress, anxiety and depression in your daily life may help you to return to your normal weight.