Weight loss

Unintentional weight loss occurs in many diseases and conditions, including some very serious diseases such as cancer, AIDS, and a variety of other diseases.

Poor management of type 1 diabetes mellitus, also known as insulin-dependent diabetes mellitus (IDDM), leads to an excessive amount of glucose and an insufficient amount of insulin in the bloodstream. This triggers the release of triglycerides from adipose (fat) tissue and catabolism (breakdown) of amino acids in muscle tissue. This results in a loss of both fat and lean mass, leading to a significant reduction in total body weight. Untreated type 1 diabetes mellitus can produce weight loss.

In addition to weight loss due to a reduction in fat and lean mass, fluid loss can be triggered by illnesses such as diabetes, certain medications, lack of fluid intake or other factors. Fluid loss in addition to reduction in fat and lean mass exacerbates the risk for cachexia.[1]

Infections such as HIV may alter metabolism, leading to weight loss.[2]

Hormonal disruptions, such as an overactive thyroid (hyperthyroidism), may also exhibit as weight loss.[3]

One cutoff value of where unintentional weight loss is of significant concern is where there's a weight loss of more than 5% in the past month, or at least 10% during the last 6 months.[4]

[edit] Causes of unintentional weight loss
Starvation, a state of extreme hunger resulting from lack of essential nutrients over a prolonged period.
Cancer, a very common and sometimes fatal cause of unexplained (idiopathic) weight loss. About one-third of unintentional weight loss cases are secondary to malignancy. Cancers to suspect in patients with unexplained weight loss include gastrointestinal, prostate, hepatobillary (hepatocellular carcinoma, pancreatic cancer), ovarian, hematologic or lung malignancies should be considered in any patient presenting with unexplained weight loss.
AIDS can cause weight loss and should be suspected in high-risk individuals presenting with weight loss.
Gastrointestinal disorders are another common cause of unexplained weight loss - in fact they are the most common non-cancerous cause of idiopathic weight loss. Possible gastrointestinal etiologies of unexplained weight loss are celiac disease, peptic ulcer, inflammatory bowel disease (crohns disease and ulcerative colitis), pancreatitis