Weight loss and fatigue are generally thought of as falling into one of several categories that help doctors think rationally about what disease process may be causing these symptoms. Cancer is always considered when someone presents with weight loss and fatigue; however, a wide variety of other causes, including viral infection and other illnesses, may be causing these symptoms. A variety of treatments may be utilized to alleviate weight loss and fatigue; these are instituted after a thorough medical workup.
About Weight Loss and Fatigue
According to Ralph Gonzales and Paul L. Nadler in "Current Medical Diagnosis and Treatment," fatigue generally falls into one of three categories: generalized weakness, or problems beginning tasks; easy tiring after beginning a task; and mental fatigue, or difficulty concentrating. Weight loss is generally one of two types: voluntary weight loss, which is associated with diet and exercise, is not medically concerning; involuntary weight loss, which is a loss of at least 5 percent of a person's body weight over at least six months when he is not trying to lose weight, is medically concerning.
Sudden Weight Loss and Fatigue
According to Carol Reife in "Harrison's Principles of Internal Medicine," while cancer must be in the differential diagnosis of anyone presenting with weight loss and fatigue, cancer tends to cause slower-onset, chronic symptoms instead of sudden symptoms. Sudden symptoms suggest that something new, such as an infection, might be causing the symptoms. Infections that can cause sudden weight loss and fatigue include hepatitis and HIV.
According to the Mayo Clinic, a particularly severe presentation of a chronic disease might cause sudden weight loss and fatigue. Examples of diseases that might present in this way include certain metabolic conditions such as diabetes and hyperthyroidism and gastrointestinal disorders such as Crohn's and celiac disease. Psychiatric disease, including depression and dementia, can also cause weight loss and fatigue.
Approach to Diagnosis
According to Carol Reife, the first step is to confirm that weight loss has actually occurred. This can be accomplished using previously collected weight measurements, or by noting that clothes which previously fit well have become too loose. A history and physical should be performed that focus on causes of weight loss, including chronic disease, infections, cancer, metabolic disturbances and so on. Laboratory testing will be directed by the results of the history and physical exam, but might include a complete blood count, a thyroid test and a urinalysis, among others.
The treatment of sudden weight loss and fatigue will depend on the cause. For example, if cancer is causing your weight loss and fatigue, treatment is usually surgical removal coupled with chemotherapy or radiation therapy. In contrast, if a new viral infection is the cause, treatment consists of appropriate antiviral medications, and if mental illness is the cause, treatment may consist of pharmacologic and behavioral therapy aimed at altering that disease.