[presscast]

>Frail elderly people often don't eat enough, or lack fiber, for example because their teeth hurt. Appetite also declines with age.

You're strongly implying causation here. I'm unaware of any serious body of research that indicates elderly people are getting frailer because of a decrease in appetite.

[adrianN]

I did not mean to imply that, I just wanted to make the point that eating less is not always good advice, in particular in the age bracket that suffers from age related muscle loss.

[doctorcroc]

You're right, and there's always exceptions to the rule. Eg some of those with life threatening injuries probably need processed food in the interim. But the general point stands which is that human longevity had been correlated with caloric restriction. Even in Ben Franklin's wit and wisdom, he remarks that to preserve one's life, one should eat less. This observation is timeless

[atomical]

Human longevity has also been correlated with many other things.

https://en.wikipedia.org/wiki/Blue_Zone

[adrianN]

I don't think caloric restriction has been shown to increase lifespan in humans. It works very well in the mouse model, but iirc monkeys don't benefit (as much?).