Urban caveman movement
The urban caveman movement is a recent lifestyle fad (circa 2010) involving what appear to be elements of the caveman diet, the early 1990's men's movement, frequent fasting to mimic the long stretches paleolithic people might have gone between meals, and a lot of broscience. It is in part a bodybuilding and fitness fad. Urban cavemen go so far as to frequently donate blood (to mimic the many injuries a caveman might incur), and engage in barefoot running and "hunting and gathering" in city parks. They do not, however, seem to show any inclination to give up their cars, computers, plumbing, electricity, access to modern medicine, nor the refrigerators they keep their raw venison and fresh berries in. 
Further information on this ridiculous woo will be reported as it develops.
"Modern primitives" are a closely related subculture who engage in extensive, ritual body modification (piercings, tattoos, scarification, play piercings, flesh hook suspension, etc) combined with a desire to emulate primitive cultures in an urban setting. It is highly advised to avoid this movement if you have a low tolerance for pain.