> that might not get repaid

This is the part that we know is false. The benefits outweight the costs. But fine, suffer if you want.

This research exists. This study [1] suggests a 2.7 year increase in life expectancy. Doing some math, 5 minutes per day for 80 years is around 0.2 years.

So sure I might have gone fishing a bit to respond to a random HN comment but the data is out there and you have a brain.

[1] https://pubmed.ncbi.nlm.nih.gov/9794712/

I really don't think "walk briskly for five minutes a day" is a health nut thing. That sounds more like the advice your doctor gives you when she knows you won't do anything a health nut says.

If you are waiting for studies that perfectly model every variable before you spend 5 minutes walking, you are unlikely to be satisfied within your rapidly decreasing lifespan.