By measuring the length of your “telomeres”, the ends of chromosome.
Basically, telomeres allow our cells to divide. When we’re young, our telomeres are long, and we can produce new cells with ease.
As we age, our telomeres shorten, and it is harder to produce new cells. With fewer new cells to replace the older ones, we age.
As the New York Times’ Gretchen Reynolds explained last year:
Telomeres are tiny caps on the end of DNA strands — the discovery of their function won several scientists the 2009 Nobel Prize in medicine. When cells divide and replicate these long strands of DNA, the telomere cap is snipped, a process that is believed to protect the rest of the DNA but leaves an increasingly abbreviated telomere. Eventually, if a cell’s telomeres become too short, the cell ‘‘either dies or enters a kind of suspended state,” says Stephen Roth, an associate professor of kinesiology at the University of Maryland who is studying exercise and telomeres. Most researchers now accept telomere length as a reliable marker of cell age. In general, the shorter the telomere, the functionally older and more tired the cell.
The University of Texas Southwestern Medical Center at Dallas, Department of Cell Biology and Neurosciences proved in 1996 the basic hypothesis using cell cultures: Click here to read the full article