New horizons in appetite and the anorexia of ageing

Appetite drives essential oral nutritional intake. Its regulation is complex, influenced by physiology, hedonism (the reward of eating) and learning from external cues within a person's society and culture. Appetite loss is common in the older population and not always attributable to medical conditions or treatment. Although the physiological basis of the anorexia of ageing (loss of appetite due to the ageing process) has been established, the effect of ageing on hedonism and external cues, which may be equally important, is less well understood. The anorexia of ageing is associated with reductions in dietary diversity and oral intake, and increased risk of malnutrition, sarcopenia and frailty. Early identification of poor appetite could allow timely intervention before weight loss occurs. There is no standardised tool for assessing appetite in clinical settings at present but the 4-item Simplified Nutritional Appetite Questionnaire (SNAQ) has the potential to be used in this way. This review, designed for clinicians, will discuss the regulation of appetite and the pathogenesis of the anorexia of ageing. It will describe the current evidence for interventions to manage the anorexia of ageing, which is limited, with little benefit reported from individual studies of education, physical activity and medication. There is some positive evidence for flavour enhancement, fortified food and oral nutritional supplements but mainly within single studies. Looking ahead, the aim is to develop multicomponent approaches to the treatment of the anorexia of ageing based on growing understanding of the role of physiological signalling, hedonism and external cues.