At about what time in life do we start aging, as in our body starts to slowly deteriorate?

Probably in our 30s is when it starts to progress. People often develop neck issues in their 30's and most people will have some sort of spine pain or issue at some point in life. This is why it's great to exercise and keep our bodies strong.

The human body starts aging around age 40. But 60 is the new 40 nowadays, people live longer, & look younger than people did 100 yrs. ago. There are lots of actors in their 50s, who still look really young, & really hot. :)

Well mine started going down hill about 5 years ago after I finished building this house. Before that I could go and blow all day doing wiring, framing, plumbing etc. Oh to be 76 again.

after 40, you will feel it