Longevity

101 Facts About Ageing #49: Appetite and Ageing

Posted on 4 November 2021

As Daniel Patrick Moynihan, an American sociologist, politician, and diplomat once said: “Everyone is entitled to his own opinion, but not his own facts”. And we wholeheartedly agree. A shared set of facts is the first step to building a better world with longevity for all. In that spirit, we are creating a series that covers 101 indisputable facts about ageing, health and longevity.

Ageing is associated with a loss of appetite, a common but sometimes overlooked problem among the elderly that contributes to nutritional deficiencies, weight loss and poor health. This has been referred to as ‘anorexia of ageing’ (AA), defined as a decrease in appetite or food intake in old age. Meta analyses suggests that it affects between 15% and 30% of over 65s who don’t live in care homes (the average sufferer of anorexia of ageing is in their early 80s). Being female, living in a care home, and increasing age are all associated with greater probability of having AA. Some studies suggest that people with AA are 45% more likely to die on average compared with those without, and those whose AA is accompanied by weight loss are 83% more likely to die. However, much of this increased risk may not be due to the anorexia itself but due to other confounding factors: for example, loss of appetite could easily be a consequence rather than a cause of other health problems.

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A summary of factors influencing appetite and how they change with age. Red arrows represent factors that decrease appetite, green arrows represent factors that increase appetite.
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Appetite decline with age is caused by a combination of factors: a decreased daily energy expenditure with age is responsible for some appetite loss, and this is not necessarily a bad thing. Much of the decline in appetite may come from decreased enjoyment of food due to factors like a reduced sense of taste, smell and even vision, reduced saliva production, dental problems and digestive problems. In the elderly, food also tends to remain in the stomach for longer, which prolongs the sensation of fullness after a meal.

Hormonal changes also have a role to play. For example, studies suggest that in older people, levels of ghrelin (the ‘hunger hormone’) are lower than in young people outside of mealtime, while levels of the ‘satiety hormone’ leptin are higher.

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Average levels of acylated ghrelin in 11 young subjects and 11 elderly subjects before and after before and after a meal eaten at time 0.
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While proving the direction of cause and effect is challenging, it is highly likely that there is a two-way relationship between most chronic diseases of ageing and appetite loss. That is to say that chronic diseases such as cancer, heart disease and dementia lead to a loss of appetite (as can their medications), and a loss of appetite leads to nutrient deficiencies that make chronic diseases more likely. Chronic diseases impact appetite primarily through the release of inflammatory molecules, which influence activity in areas of the brain controlling food intake, and by causing nausea.

Finally, not to be overlooked are the psychological and social aspects of eating and their effects on appetite. Elderly people are more likely to eat alone because they are more likely to live alone and less likely to engage in social activities. This may reduce the enjoyment associated with food.


References

An overview of appetite decline in older people: https://dx.doi.org/10.7748%2Fnop.27.5.29.e697

Signals generating anorexia during acute illness: https://doi.org/10.1017/S0029665107005587

EFFECT OF AGE ON THE DYNAMICS OF ACYLATED GHRELIN IN FASTING CONDITIONS AND IN RESPONSE TO A MEAL: https://doi.org/10.1111/j.1532-5415.2008.01732.x

The anorexia of ageing: physiopathology, prevalence, associated comorbidity and mortality. A systematic review: https://doi.org/10.1016/j.maturitas.2013.01.016

Physiological and psychosocial age-related changes associated with reduced food intake in older persons: https://doi.org/10.1016/j.arr.2012.08.002

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