Adulthood was what did it for me. : - ) I'm theorizing that it's at least 2 factors: lack of PE (2.5h a week of forced exercise - gone), & reaching legal drinking age (I lost the most weight when pausing drinking for a bit). There were also random occasions for physical activity that now require more effort to set up that were handled by adults in my life or otherwise organized by someone else (skiing trips, hiking, kayaking).