Here are two great papers, cycles1(pdf) and cycles2(pdf), that show where my thinking has been headed lately. Both papers are coauthored by Frank Booth, and they attempt to connect eating and exercising to Paleolithic cycles and conditions.
Here's a quote from the first paper: "Consequently what is called the mechanisms of skeletal muscle hypertrophy from sedentary levels today would probably be the maintenance of muscle mass in the Late Palaeolithic era." This puts a different spin on resistance training. Instead of it being something that people should do, or could do to build muscle, it is more what we are meant to do - lift heavy loads on a regular basis.
Here's another great quote: "Pre-diabetic conditions occur within 5–10 days of reducing physical activity levels in healthy humans. Thus, reduced physical activity is associated with a rapid development of insulin resistance." Again, the shows that regular physical activity is natural and "expected" by the body, and that sedentary living quickly becomes dangerous in terms of health.
