Typically, research on aging is done in older people. The problem with studying aging in old people is that most of them already have age-related diseases, which anti-aging interventions aim to prevent.
Age-related changes in the body start to accumulate early in life and affect physiological function years before disease diagnosis; atherosclerosis is a prime example. Thus, intervention to reverse or delay the development of age-related diseases must be done while people are still young , before aging-related diseases become established.
Up to this point, the main obstacle to studying aging before old age and before the onset of age-related diseases has been the absence of methods to quantify the pace of aging (i.e. aging rate) in young people. However, a recent study shows that aging processes can be measured in people still young enough for prevention of age-related disease, and that physical manifestations of aging are already present in young adults.