“as a population that thin people in their 60’s are remarkable”
I am not thin by any means.
I am 5’8”, 180lbs with relatively low body fat.
This was not always the case. I had packed on the pounds over the years.
About 4 years ago I thought I would try pushups. I had a sit down computer job for 30 years. I lifted some weights, but had a hard time keeping an exercise schedule working 60-70 hours a week.
I could only do 1 pushup. So I started doing pushups 3 times a week when I would get home from work.Worked my way up to 5 pushups. Then started adding 5 pushup sets. When that became easy I started doing sets of 10.
4 years later I now do one set of 200 and 10 to 20 minutes later I do another set of 250. I backed of, because doing 3 sets of 200 caused me to be tired the rest of the day.
Took me many months to figure that one out. Dooh. Too vigorous.
In that time I changed my diet to be more whole food based. Plenty of meat. Less refined carbs. More fresh veggies.
I lost 30 pounds of fat. Also added many pounds of muscle. went from a 38 to a 33 waist too. I am in my 60’s and I am in the best shape of my life. I also wear my old belt from 1975. It's awesome and the wife has watched me and started losing weight to. We are like a couple of teenagers again.
I was forced to retire couple of years ago, so time is not an issue.
But in the end, you must do what works for your body type. And remember, it really doesn't matter what anyone else thinks about it, you are doing it for yourself.