I've spent large chunks of my life as an extremely fit ultra-endurance athlete. I've done events that other ultra-endurance athletes called "insane". I wasn't at the front of the pack, but I was at the front of the middle of the pack.

These days, I'm not interested in racing. I'm not even interested in training. But if I do think about "fitness" or "health" goals, it's definitely structured around what I'd like to be able to do, rather than specifics of my body.

For example, one standing goal I've had for a long time is to remain fit enough be able to go out and run a half-marathon more or less on a whim, and still finish in 1:45 or less without hurting too much.

More recently, having moved to 6000' as a home elevation, as well as being very sedentary from work/life stuff, I'd like to be able to keep up runs uphill without stopping, regardless of the pace I'm moving at (currently impossible).

I think structuring things around "what I want to be able to do, and how I want to feel after I do them" is an excellent framework, and far better than "lose N pounds" or "cut X minutes off my time for Y".