Maybe you’ve noticed by observing your own parents or grandparents, older people don’t like to eat. My mother used to say of her mom, “she eats like a parakeet.” This is part of the reasons sarcopenia and loss of function occurs – too few calories and other nutrients are consumed, so the body can’t maintain its status quo.
Loss of appetite may become common (11) and there are only a few things that can be done about it beyond being conscious and eating more than you may be content with.
Changes in hunger hormone levels and pleasurable sensations from food are affected by advancing age (12). Not a whole lot can be done to alter this (apart from exercise of course, which we know you’re already doing). However, hunger is also affected by psychosocial parameters that are modifiable.
Common in elderly are mood disturbances, such as depression, apathy, loneliness, and environmental changes. Each of these factors decreases appetite, so it is important to keep up your social health (12). This is easier said than done, and it may not become relevant in your forties, fifties, or even sixties, but when the seventies, eighties, and nineties creep in, keep this in mind.
Also keep an eye on your fluid intake. Thirst detection is controlled by the brain, but these receptors become desensitized with old age, and this can be coupled with impaired fluid regulation by the kidneys, leading to an even worse situation (13, 14).
Experienced athletes don’t need to be told twice that dehydration is bad news bears, so I won’t harp on this point too much. Drink enough water and other fluids to stay hydrated and prevent fatigue and loss of function.