Yep, by definition metabolism is the sum of all chemical reactions in an organism! It's like the confusion with hypothesis and theory in media today, metabolism has basically been neutered the same way.

True, but it isn’t just about fast or slow.

This is true, as @shreddy_scientist@lemmy.ml pointed out it's all of it, both the kind and the volume over time. What I wanted to challenge with my comment is the misconception that many of the adaptations, which affect our metabolisms, triggered by physical exercise are no longer accessible when we get older. Which is not incorrect, but the degree to which I notice this belief being held to, usually is. Also, as far as exercise goes, strength or skill training might decline noticeably (depending on the level each one of us took advantage of our youth) with age, but endurance training, if done properly, will not, at least not significantly or very early. In the context of the original post and article that focuses on CVD, this is quite optimistic.

If you examine proper running form it makes sense to see people in their fifties and sixties running good times on marathons and ultra-marathons. So it is a habit that can support quite good health conditions even later in life. Also, on the same note, another inspiring example from an endurance training perspective.

But this is where my mind went when I read your sentence about habits sustaining a persons health, mostly because I tend to think that our bodies are designed to move quite a lot and food comes second to activity, to assist and support the adaptations and to fuel the movement. Your last examples make me think that you were referring to eating habits alone, so I probably misread your original comment, sorry :-)