I'm still 5 + years away, but best I got is:
Eat real food. Not too much. Mostly plants.
Exercize daily. Have variety. Do intervals.
Specifically-Pilates, and anything balance related works the core.
Ultimately though, the most important thing is to love our bodies for what they can do-6 pack abs or no. We should have gratitude for all the ways we can move, not having pain, not having illness-because we (self included) take that for granted, until we do have health issues.
Also, I suspect the weight probably serves a protective function, in case we have falls. Not looking forward to it and will probably gripe about it though!