OP, your aims are laudable but a bit confused. There's a limited amount that either exercise or diet can do for body shape itself, but a combination of both is important for overall physique, weight & general fitness.
I'm 47, exercise daily at 6 am & am active throughout the day. I combine cardio, weights & core; I run, do HIIT & Spin, and weights are incorporated into my gym sessions. I eat well, overall - no junk or takeaways, but can skip meals & eat randomly to make it up. I'm genetically fortunate that I come from a slim family - I've slim, less fit siblings who do barely any / no exercise, unfairly!
I exercise for my physical & mental well-being. It's really important to me. I do like the effect on my body. I also understand what works for my body & adapt to that, and that's vital for everyone.
You've a lot of misunderstandings in your posts though!
i do not think running is good for waists in middle age as it stores stress hormones and therefore fat around the middle.
Completely untrue. Any form of activity is good for our bodies & physique. Not everyone likes running through, and not *everyone runs effectively. But anyone running at a reasonable pace, regularly, will not store fat on their middle. However, they won't build up core / muscle strength, and it can be unforgiving on joints.
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I combine running, therefore, with other exercise.
This again. Cardio doesn’t burn far it stores it. A tip for us all.
Not true. It is the case that exercise is defined as 'fat burning' or 'cardio' but actually, if you are engaged in sufficiently vigorous cardio activity, you will burn fat. For weight loss, diet is a chief consideration though.
Middle fat is visceral fat and that's bad for heart etc
Fat around the middle is of concern due to the proximity to major organs. But visceral fat refers to fat around organs, internally, which even skinny people can have.
it’s kettlebells and HIIT that seems to work best
This is cardio.
It's not that they work 'best'. It's that benefits can often be seen by high-intensity exercise that raises your heart rate. Running or similar can be hard to achieve this, as if you are unfit it will take a while to be able to run for sufficient distance / intensity, you'll just stop. With HIIT sessions, it's short bursts of intensity which the body responds well to.
I think you might be overthinking a lot of this. Find exercise you enjoy, do it regularly & until you are out of breath, in life weights & core (properly supervised).