Gastrointestinal hormones: the regulation of appetite and the anorexia of ageing
Loss of appetite is frequently observed during ageing, termed the ‘anorexia of ageing’. Ageing is associated with the inability to appropriately increase food intake after under‐eating in the short‐ and long‐term. Older people also report lower feelings of hunger and increased feelings of satiety and fullness. Gastrointestinal peptide hormones are a major part of the appetite regulatory system and are released in response to nutritional stimuli. They can be classified as: anorexigenic (satiety) [e.g. peptide tyrosine tyrosine (PYY), glucagon‐like peptide‐1, pancreatic polypeptide, oxyntomodulin and cholecystokinin (CCK)] or orexigenic (hunger) (e.g. ghrelin). Although the control of appetite is not fully understood, it is clear that these hormones play an important role, and may influence the development and treatment of obesity and under‐nutrition. The literature shows a consistent finding that there is a loss of appetite in those aged over 65 years, although how this loss is mediated is not yet clear. Some evidence suggests that with advancing age there is an increase in satiety hormones, such as CCK and PYY, and a decrease in the hunger hormone, ghrelin. However, not all studies agree, emphasising the need for more in‐depth research to clarify age‐related changes. This knowledge will enable us to develop therapies to help prevent under‐nutrition during ageing. This review explores how age influences gastrointestinal appetite hormones in humans, as well as how this may contribute to the development of age‐related malnutrition.
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