More exercise correlates with younger body cells.

Reynolds points to work by Loprinzi et al. showing physicaly active people have longer telomeres at the end of their chromosomes' DNA strands than sedentary people. (A telomere is a region of repetitive nucleotide sequences at each end of a chromatid, which protects the end of the chromosome from deterioration from from fusion with neighboring chromosomes. It's length is a measure of a cell's biological age because it naturally shortens and frays with age.) Here is their abstract, complete with three (unnecessary) abbreviations, LTL (leukocyte telomere length), PA (physical activity) and MBB (movement based behaviors), that you will have to keep in your short term memory for a few seconds: 

INTRODUCTION: Short leukocyte telomere length (LTL) has become a hallmark characteristic of aging. Some, but not all, evidence suggests that physical activity (PA) may play an important role in attenuating age-related diseases and may provide a protective effect for telomeres. The purpose of this study was to examine the association between PA and LTL in a national sample of US adults from the National Health and Nutrition Examination Survey.  

METHODS: National Health and Nutrition Examination Survey data from 1999 to 2002 (n = 6503; 20-84 yr) were used. Four self-report questions related to movement-based behaviors (MBB) were assessed. The four MBB included whether individuals participated in moderate-intensity PA, vigorous-intensity PA, walking/cycling for transportation, and muscle-strengthening activities. An MBB index variable was created by summing the number of MBB an individual engaged in (range, 0-4).  

RESULTS: A clear dose-response relation was observed between MBB and LTL; across the LTL tertiles, respectively, the mean numbers of MBB were 1.18, 1.44, and 1.54 (Ptrend less than 0.001). After adjustments (including age) and compared with those engaging in 0 MBB, those engaging in 1, 2, 3, and 4 MBB, respectively, had a 3% (P = 0.84), 24% (P = 0.02), 29% (P = 0.04), and 52% (P = 0.004) reduced odds of being in the lowest (vs highest) tertile of LTL; MBB was not associated with being in the middle (vs highest) tertile of LTL.  

CONCLUSIONS: Greater engagement in MBB was associated with reduced odds of being in the lowest LTL tertile.