Unexplained weight loss occurs for a variety of reasons, ranging from unhealthy eating and poor nutrition to diseases and aging. When you lose weight without trying and begin to lose hair as well, you may be at risk for a serious medical condition, according to Medline Plus. Family members, caregivers and health care professionals must monitor others for sudden weight loss and thinning hair when they suspect mental illness or self-inflicted harm.
Mental disorders that lead to malnutrition and weight and hair loss include anorexia nervosa and bulimia that occur when a person has an unrealistic body image and an intense fear of gaining too much weight. People suffering from eating disorders often find ways to hide their weight and hair loss and refusal to eat. Drug addiction and alcoholism are other conditions that can lead to unexplained weight loss and thin hair, according to Medline Plus. Depression is a common mental disorder that affects the elderly and causes unintentional weight loss and reduced hair growth.
Hyperthyroidism is a disease that results in extreme weight loss, even when the patient eats plenty of calories. When cancer cells rage through the body, unintentional and unexplained weight loss can occur. Hair loss often results from cancer treatments such as chemotherapy and radiation. Chronic diarrhea and AIDS are two other diseases commonly associated with unexplained weight loss and thinning hair.
When diseases such as AIDS or cancer cause unexplained weight loss, other side effects typically are present. In many cases, the disease can first be recognized because of the sudden loss of weight or unexplainable hair loss. According to the Mayo Clinic Cancer Center, symptoms and side effects also can be misread, leading to a late diagnosis. For example, side effects of lymphoma often include fever, fatigue and night sweats in addition to the weight loss. Infections cause fever, chills, weight loss, fatigue and night sweats in people with AIDS.
Stress, hormone changes and some medications often manifest side effects such as hair loss and unexplained weight loss, according to Merck. Fungal infections and other immune-compromising illnesses can result in alopecia, or hair loss and a sudden drop in weight. Systemic conditions such as lupus, endocrine disorders, food intolerances and digestive disorders can lead to the two symptoms.
Sometimes doctors can diagnose the cause of hair loss by examining the pattern of baldness and taking a family history. Blood tests, hair sample tests and biopsies can help doctors determine infections and other system-wide diseases. Close monitoring and honest discussion with a physician can reveal behaviors or thought processes that lead to the weight and hair loss.