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Anorexia and Weight Loss


Anorexia is a medical term used to describe loss of appetite, it may be transient, lasting a few hours or more sustained, lasting for months or even years. If sustained it anorexia often leads to weight loss. Loss of appetite may have many causes, psychological as well as physical. Patients with cognitive decline may simply forget to eat, or lose the normal  drives that lead to hunger. Anxiety may manifest as a feeling of nausea that inhibits normal eating by its effect on satiety. Equally systemic physical illness, outside of the gut can have profound effects on our urge to eat mediated through the inflammatory proteins such as interferon that make us feel unwell and not “much like eating”.  A classic example of such weight loss would be that seen in some patients with advanced cancer or tuberculosis (formerly known as galloping consumption). Gastro-intestinal disease may cause weight loss through a direct effect on the capacity of the gut to either contain or digest and absorb food. As well as this it may also ead to the release of proteins and hormones that directly influence appetite and satiety.

When anorexia and loss of appetite occur and there is a clear cause identified it is important to ensure proper nutritional intake is not compromised, whilst addressing the underlying cause of the problem. When significant unintentional weight loss arises this should always provoke reflection on possible triggers and causes and consideration of whether and what dietetic interventions may be indicated.

Weight loss

Significant unintentional weight loss is defined as a loss of more than 5% of normal body weight over a period of less than 1 year. Normal body weight does vary from day to day by as much as 2-3%, either way due to changes in fluid balance. So for a 100kg man a drop to 97kg over 24 hours or an increase to 102kg would not be unusual. This is because intake of fluid and food as well as urination, sweating and defaecation all impact upon our weight day to day. However unintentional sustained and persistent weight loss is not normal. It usually results from reduced intake due to a combination of anorexia and or early satiety or a sustained change in eating patterns or lifestyle.

On occasion it may reflect increasing caloric expenditure either due to caloric loss as a result of increased energy expenditure (often exercise), loss of sugars in the urine (untreated diabetes) or  increased metabolic rate (hyperthyroidism). It may also result form decreased absorption of ingested (eaten) calories because of maldigestion (pancreatic disease) ir malabsorption, but the gut has significant spare capacity so this is often only a minor factor. Most commonly  unintentional weight loss reflects reduced intake due to a combination of early satiety or anorexia, or both these factors combined.

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