Dysregulated gut hormone responses to nutrient ingestion in older adults with low appetite: a mechanism of anorexia of ageing

Anorexia of ageing - the age-related reduction in appetite and food intake - is a public health concern for an ageing global population. However, current understanding of the aetiology of the condition is limited. In this review, evidence of gut hormone responses to feeding in older adults is reviewed, and it is proposed that a dysregulation of this process is a mechanism driving low appetite in later life. The evidence is synthesised to critically present this case, spotlighting recent data demonstrating a highly anorexigenic gut hormone profile in older adults exhibiting low appetite, which is not observed in older adults exhibiting a "healthy" appetite. These findings and this theory are interrogated with an appreciation that appetite control is complex and multifactorial, not least in the context of anorexia of ageing; it is posited that changes in gut hormone secretions are <i>a</i> mechanism rather than <i>the</i> mechanism, but propose that this may explain certain presentations of anorexia of ageing. The current knowledge base is contextualised for practical implications and priorities for future research are highlighted.