This thread is pretty interesting. I'm 51 and have the same size waist as I did when I was in college. I hate the gym and I hate working out but I am there all the time. That's how manage to keep in shape esp. in the non riding months which are pretty long here in central Indiana I protein supplement pretty often but don't go crazy with it. My diet is decent overall so I supplement with maybe1 shake a day. I recently cut quite a bit of carbs and calories and dropped about 10 pounds which allowed me to achieve visible ab muscles for the first time in about 8 years.
I like beer so that didn't last very long LoL.
One thing that keeps me in the gym was a saying I read somewhere but now forget. " Strong people are harder to kill" , That's motivating enough for me !!