>>11368040All these replies and no one even mentions telomere shortening. When our telomeres get shorter, cells can no longer reproduce and our tissues degenerate and die. The more a cell replicates, the shorter our telomeres get. This is why we can quantify the maximum possible lifespan for humans to be around 125 years.
Individuals who experience chronic stress are shown to have shorter telomere length compared to those with mild to no stress. Some theories as to why this could be include lack of sleep (less efficient cellular repair) and the constant release of adrenal gland chemicals altering DNA methylation (epigenetics). Experiments do show that both resistance and aerobic exercise will slow down telomere shortening though. It is still inconclusive if exercise can reverse the shortening that already occurred, but it does seem to be one of the only provable ways to slow down the aging process and combat stress.
My personal thoughts are that because exercise technically is inducing periods of constant stress, and exercise is confirmed to slow down telomere shortening, it is more so the indirect consequences of stress causing the rapid aging in people. Lack of sleep, poor nutrition, growth of the amygdala through increased trace amine demands, etc. Get more sleep, eat better food, meditate and most importantly exercise. Basically all of the things doctors have been telling us for years.
A recent randomized control trial for reference:
https://www.ncbi.nlm.nih.gov/pubmed/30266522 
