It is a decrease in body weight resulting from either voluntary (diet, exercise) or involuntary (illness) circumstances.
Unexplained weight loss that is not caused by reduction in calorific intake or exercise is called cachexia and may be a symptom of a serious medical condition. For other uses, see Weight loss (disambiguation) . Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon, and other connective tissue. Definition. Unexplained weight loss, or losing weight without trying — particularly if it's significant or persistent — may be a sign of an underlying medical disorder. The point at which unexplained weight loss becomes a medical concern is not exact. But many doctors agree that a medical evaluation is called for if you lose more than 5 percent of your weight in six months to a year, especially if you're an older adult. For example, a 5 percent weight loss in someone who is 160 pounds (72 kilograms) is 8 pounds (3.6 kilograms). Examples of involuntary weight loss include the weight loss associated with cancer, malabsorption (such as from chronic diarrheal illnesses), and chronic inflammation (such as with rheumatoid arthritis). Weight loss: Weight loss is a decrease in body weight resulting from either voluntary (diet, exercise) or involuntary (illness) circumstances. Most instances of weight loss arise due to the loss of body fat, but in cases of extreme or severe weight loss, protein and other substances in the body can also be depleted There are 43 conditions associated with recent (short-term) memory loss and weight loss (unintentional). The links below will provide you with more detailed information on these medical conditions from the WebMD Symptom Checker and help provide a better understanding of causes and treatment of these related conditions.  Unintentional weight loss may result from loss of body fats, loss of body fluids, muscle atrophy, or even a combination of these. It is generally regarded as a medical problem when at least 10% of a person's body weight has been lost in six months or 5% in the last month. For other uses, see Weight loss (disambiguation) . Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon, and other connective tissue. Some of the comorbid or associated medical symptoms for Sudden onset of weight loss may include these symptoms: 1  Abdominal symptoms. 2  Chronic Crohn's-like symptoms. 3  Chronic Crohns-like abdominal symptoms. 4  Chronic ibd-like abdominal pain. 5  Chronic ibd-like symptoms. 6  Chronic ibs-like abdominal pain. 7  Chronic ibs-like symptoms.  Weight loss (unintentional). WebMD Symptom Checker helps you find the most common symptom combinations and medical conditions related to weight loss (unintentional). Click on the combination that matches your symptoms to find the conditions that may cause these problems. 
https://en.wikipedia.org/wiki/Weight_loss http://www.mayoclinic.org/symptoms/unexplained-weight-loss/basics/definition/sym-20050700 http://www.medicinenet.com/script/main/art.asp?articlekey=53393 http://symptomchecker.webmd.com/multiple-symptoms?symptoms=recent-(short-term)-memory-loss%7Cweight-loss-(unintentional)&symptomids=513%7C257&locations=66%7C66 https://en.wikipedia.org/wiki/Weight_loss http://www.rightdiagnosis.com/sym/sudden_onset_of_weight_loss.htm http://symptomchecker.webmd.com/single-symptom?symptom=weight-loss-(unintentional)&symid=257
sudden weight loss medical term