According to the Mayo Clinic, any significant weight loss without a change in the diet or exercise routine is cause for concern as it can signal an underlying medical condition that needs to be addressed. Possible causes of unexplained weight loss include cancer, Crohn's disease, diabetes, hypercalcemia, Parkinson's disease, heart failure, HIV, hypothyroidism, hyperthyroidism, tuberculosis and ulcerative colitis.
Any weight loss of 5 percent of the total body weight or over 10 pounds in a six- to 12-month period is considered a significant unexplained weight loss and is reason to schedule a doctor's appointment for evaluation, according to the Mayo Clinic. At an appointment, a doctor takes a history, performs a physical examination and orders further testing as needed to determine the cause of unexplained weight loss. Based on the situation, a doctor works with the patient and her particular needs to arrange a special diet or other considerations to prevent further weight loss. Calorie intake, age, overall health and nutrient absorption are among the factors that determine body weight. While small fluctuations are normal, and the loss of a few pounds is typically not a cause for concern, larger losses of weight are an indication of a problem in the body.