Strength coach Dan John wrote with regards to training, "Once you make it to 25, you'll make it to 55, almost no matter what you do. Fifty-six is when the statistics punch you in the face. Fifty-six is when the guy knocks on the door and says, "it's time to pay the piper.'"
But the problem for most people starts much earlier. That guy knocks on your door will have a lot to do with how you trained and took care of your body from 30 to mid-'50s.
From 30 on, our body starts to change slowly, slower metabolism, decreased muscle mass, increase in body fat composition. It's the natural progression of aging.
However, the key is to getting into a program as early as possible with the understanding that you are preparing for when that guy comes knocking at your door; it's not the first time you've thought about training and taking care of your body.
If you wait that long, especially with lack of prioritizing your training and health, the road is much harder.
Instead of maybe modifying some exercises and continuing to be relatively strong, mobile, and fit, your training will be focused on how to keep it together physically so you can survive.
I always tell my adult clients the key to aging well is not stopping. Training is something you have to commit to, and the earlier you can do it, the better.
The initial motivation may be to look good, but what's more important is being a strong, fit, healthy, and physically capable human being.
Training must be a priority. Don't wait until it's too late.
Take care of it now. It doesn't have to be anything crazy. You don't have to do CrossFit, boot camps, HIIT classes or hire trainers that make you feel like you have to die in your workouts.
Do some progressive strength, mobility, cardio, and vary the intensity throughout the year.
Make it your goal to be able to pick heavy things up off the ground, lift heavy things over your head, be able to run a mile (start with a 1/4 mile) without dying, and be able to get off the ground without touching every body part. Keep the mindset of always being fitter than your age.
I have some pretty amazing clients in their 50's and 60's who are doing things most 30 years olds I know can't do. It's because they've made training a priority and part of their lifestyle.
I'd love to help you with this if you want as well through my in-person training or app.