I also lost weight, mostly out of stubbornness. We were sitting at the dinner table and people were making fun of my "mathleticism", I responded by jokingly saying that I could be super athletic if I chose to, and my sister then said she'd give me $1000 if I ever became "athletic". She still hasn't paid me. They still make fun of me, except now for going "from mathlete to athlete". So really I didn't accomplish much.
Yeah, I started to notice warning signs, like I'd walk a single city block and my feet would be sore, or I'd get up from my chair at the office and I'd need 2-3 seconds for my hips to "get right" before I could walk.
All of those added up to me committing to get into better health. Achieving some lifelong dreams along the way was just a side benefit.