Emaciation (/ᵻˌmeɪʃiːˈeɪʃən/ or /ᵻˌmeɪsiːˈeɪʃən/) is defined as extreme weight loss and unnatural thinness due to a loss of subcutaneous fat (the fatty, or adipose tissue beneath the skin) and muscle throughout the body. It affects human beings and animals; one who is emaciated could be described as wasting away or being gaunt..