A human being normally takes 4 seconds per breath. That is 2 seconds for incoming breath and 2 seconds for breathing out. This is normal and average breathing across humans. Taking this speed of breathing , if we calculate the lung capacity for breathing throughout a life span of 100 years, a human would have breathed as per below calculations :
4 seconds = 1 breath
1 minute = 15 breaths
1 hour = 900 breaths
1 day = 21600 breaths
1 year ( 365 days ) = 7884000 breaths
100 years = 788400000 breaths
So, in a day , normally we breathe 21,600 times. Or , the other way , for 21600 breathes we have taken 1 calendar day. Our body ages by 1 day. What if we slow the process and take 8 seconds per breath ? Then for same 21600 breathes , our body would take 2 calendar days. The body clock would still be 1 day , but the calendar would be 2 days. Hence , slow breathing can expand our internal body clock, thereby aging. Is this a possibility ? Well , this is the science behind our very own Pranayama or controlled breathing.
Source : heard from a discourse
