exia is the medical term for general physical wasting with loss of weight and muscle mass due to a disease. This is also known as marasmus.
ref="https://www.emedicinehealth.com/weight_loss_and_control/article_em.htm" rel="emss" onclick="wmdTrack('embd-lnk');">Weight loss can be intentional, such as from
dieting and exercise, or
unintentional and be a manifestation of illness. Weight loss can result from a
decrease in body fluid, muscle mass, or fat. A decrease in body fluid can come
from medications, fluid loss, lack of fluid intake, or illnesses such as
diabetes. A decrease in body fat can be intentionally caused by exercise and
dieting, such as for overweight or obesity. Weight loss is normal after
pregnancy.
What Are Symptoms and Signs Related to Unexplained Weight Loss?
- Loss Of Appetite
- Fatigue
- Weakness
What Causes Unexplained Weight Loss?
The loss of weight and lack of nutrition associated with a chronic illness is referred to as cachexia. Unexplained, unintentional weight loss is often a result of illness and should be evaluated by a health care professional.
- Bowel Obstruction
- Dental Problems
- Infections (Parasites)
- Malabsorption
- Medications (Both Prescription and Nonprescription)
From 
Lung Disease/COPD Resources
References
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.