Another book on the theme of running and ageing, and the relationship between diet, metabolism, exercise, and age, plus thoughts on evolution, health, and a bit of philosophy thrown in, was published in 2021: ‘Racing the Clock’ by Bernd Heinrich. He’s a retired professor of biology of some note: now in his 80’s, back in the 1980s he set US records for 100km, 100 miles, and 24 hours; his other book ‘Why we run: a natural history’ is also worth a look as are his books on biology.