Clinicians classify frailty in a symptomatic way, looking at factors such as weight loss, weakness, walking speed, and so forth. This is a method of assessment designed for use with elderly people, but researchers here apply it to a study population that includes people in the 40-60 age range.
Image credit: Stilfehler via Wikimedia (CC BY-SA 3.0)
They find that in this range, a fair number of individuals exhibit signs of what in the elderly would be called prefrailty – meaning just a few symptoms are present, rather than a majority. One logical possibility is that this is a manifestation of a sedentary, increasingly overweight population.
Physical activity and good dietary choices (largely eating fewer calories) are required to minimize declines in capacity as time marches on. It requires greater neglect to be truly out of shape at age 40 as compared to age 60, but it is certainly possible to achieve.
Link: https://doi.org/10.1186/s12877-020-1490-7
Source: Fight Aging!