It seems to me a simple rule is: is it a topic discussed in one
of the trilogy of paleodiet books*, and how does this apply to help
me? For example, "moderate sunbathing" may not seem to have anything
to do with eating food** or diet, but in fact it does
as you find out in TPPLP.

* NeanderThin, The Paleo Diet, The Protein Power LifePlan

** if you wanted to be pedantic about it I guess, drinking water is not
   eating food

Philip Thrift
http://www.paleofitness.com