Researchers identified increased production of the "feeling full" hormone PYY in elderly women, which may explain why older adults often experience loss of appetite.
While loss of appetite in seniors can be driven by emotional issues, such as depression or grief, in many cases, no underlying cause can be found.
Previous research has suggested loss of appetite in the elderly may be down to reduced production of ghrelin - a hormone that tells humans when they are hungry.
However, the new study - conducted by Mary Hickson, professor of dietetics at Plymouth University in the United Kingdom, and colleagues - found the hormone peptide YY may be to blame.
To reach their findings - published in the journal Appetite - the researchers enrolled 31 healthy adults aged 21-92 years, of whom six were over the age of 80.
They note that one major challenge with this research was finding elderly adults free of health problems, but that this was needed in order to assess changes in appetite control, independent of illness.
All subjects were required to fast for several hours, before consuming a breakfast that contained around 660 calories.
PYY production increased for elderly adults
After participants ate, the researchers measured their levels of PYY, ghrelin, and glucagon-like peptide 1 (GLP-1) - a hormone that is responsible for reduced appetite and the release of insulin - at regular time intervals over a 3-hour period.
Additionally, subjects were asked to rate how hungry they were, how much food they thought they would eat, and how pleasant the food was to eat.
Compared with younger adults, the researchers found that adults over the age of 80 demonstrated greater production of PYY. However, there was no difference in ghrelin or GLP-1 levels between the age groups.
What is more, the older adults also reported reduced hunger, reduced prospective food intake, and found the food less pleasant to eat, compared with the younger participants.
Based on their findings, the researchers say it is possible increased production of PYY leads to reduced appetite among elderly adults, causing undernutrition and weight loss.
While further studies are required to assess PYY production in a larger population of older men and women, Prof. Hickson hails the current findings "intriguing."
"If further studies on a greater number of participants show an increased production of PYY, we can work to investigate this hormone imbalance to address, and hopefully combat, anorexia of aging."
Prof. Mary Hickson