Y’all will be saying what have I got to worry about, but hear me out.
When I first moved to the UK from NZ I was a trim toned 11st. I had been in physically active jobs (and the Airforce before that), I had completed a self-build house on 3 acres with ¾ acres of lawn to look after, and had an active outdoor lifestyle with plenty of trail-riding etc, and I rarely drink alcohol.
It wasn’t long in the UK before I had jumped up to 12st - a more sedentary job and lifestyle, and age played it’s part. I’ve also a sweet’n’pastry tooth, and someone at work has always got cake/biscuits/chokkies in. It was a slow, steady increase up to Jan last year when I topped out at 13st-4 - which doesn’t sound like much to some, but it’s 20% none the less.
I’m now back down to 12st, and a major contributor to that was having a substantial project on the go - I’m so busy and immersed with my camper truck build (to the wife’s chagrin) that I forget to snack like I do when I’m bored. Also, the cost of living at the moment, means we are less likely to have random snacks in our weekly shop.
So I guess that’s my recommendation/contribution - have a long term project or hobby that gives you agency and activity, and takes your brain somewhere away from superfluous food and drink, and mental fog (and in my case, home-sickness). I have always got some sort of project or pastime on the go in the garage - just don't neglect the missus, or a few extra pounds will be the least of your worries!