Researchers in the United Kingdom believe that peptide, a hormone that tells people when they are full, may be the cause of anorexia-like symptoms in the Elderly in which appetite decreases, sometimes corresponding to a decrease in weight. This disproves other hypotheses which suggested that this condition was due to a decrease production of the hormone which helps people to recognize that they are hungry thus encouraging them to eat.

'Anorexia of aging' is common in the elderly

Aging is frequently partnered with reduced food intake which can cause weight loss and malnutrition in the elderly. It is not uncommon for the elderly to exhibit a decreased appetite with age.

This particular condition has earned the name anorexia of aging as it does not seem to be related to any other psychological or physiological problems. Some cases of weight loss in the elderly may be the result of loneliness, depression, or grief over the loss of family members and friends as they age. Anorexia of aging has no connection to these other conditions and a cause has not been definitively identified as of yet. This condition can pose a serious issue with "15-20% [of patients] experiencing unintentional weight loss" according to Medical News Today.

Previous research suggested that the cause of this disorder may be routed in one's genes, specifically the hormone ghrelin. Ghrelin is the hormone responsible for telling people when they are hungry. Decreased production of this hormone would make it more difficult for people to identify their hunger.

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The idea behind this hypothesis was that if ghrelin was produced in lower amounts than the elderly may have a decreased ability to identify their hunger causing them to eat less and potentially leading to malnutrition and/or weight loss.

Recent research lead by dietetics profession Mary Hickson at Plymouth University in the United Kingdom has disproved this claim focusing on the peptide YY instead.

Anorexia of aging may be due to production of the peptide YY

With the help of her team, Hickson suggested that one potential cause of anorexia of aging is related to the peptide YY. PYY production is regulated by the PYY gene and is responsible for telling someone when they are full. This helps to regulate total calorie consumption. In order to see if PYY was involved in the onset of anorexia of aging, Hickson and her team collected a group of over 30 participants with a wide age range. The youngest participant in this study was only 21 while the oldest was 92. In order to eliminate the chance that difference in appetite was due to any other condition, participants underwent a thorough physical exam before the start of the study in order to ensure that none of the participants had any health problems.

During the study, participants were asked to fast before consuming a breakfast that the researchers had chosen. Before eating, people were asked to report their hunger and estimate how much they believed they would be able to eat. After they had eaten, they were asked how pleasant the food was to eat and their levels of PYY, ghrelin, and glucagon-like peptide (GLP-1) were measured. GLP-1 is another hormone that is involved in hunger regulation, telling people how much they should be eating. It also helps to regulate insulin release, helping to keep blood-sugar levels constant over time.

Researchers noticed that elderly participants tended to have higher levels of PYY than the younger participants. They found no difference in the amounts of ghrelin or GLP-1. As no difference was found in ghrelin levels, the previous idea that loss of appetite in the elderly was due to lower levels of ghrelin in the bloodstream has been disproved.