This Is the Easiest Route to Self-Improvement and a Long, Healthy Life | TIME
Eric Barker stashed this in Diabolical Plans For World Domination
The Longevity Project, which studied over 1000 people from youth to death had this to say:
The groups you associate with often determine the type of person you become. For people who want improved health, association with other healthy people is usually the strongest and most direct path of change.