I've found this a really interesting discussion, and a lot of factors have been brought up already.
I'm also of the opinion that obesity is down to genetic predisposition x environment. Chris van Tulleken's output is always interesting, as a self confessed person with genetic obesity markers, and I recognise some of what he says in myself- for example, eyeing up your companion's food in a restaurant after you've finished your own! (and I wolf my food down, which I was interested to learn is also a genetic predisposition).
I'm not overweight though(although I was in the past),although I can't seem to get below the high end of a normal BMI. I achieve this with constant annoying diets though- low carb at the moment, and intermittent fasting on a permanent basis. I can only do this because my life is stable and I have enough bandwidth, though. Cooking 2 dinners for myself and the DC is not easy, and that would be the first thing to go to the wall if life was just that bit harder.
In addition, the people around you matter. Few of my friends are overweight and nearly all of them do some kind of outdoor exercise- sea swimming, hiking, cycling etc. It's a beautiful part of the world, and outdoor leisure is enjoyable and easy.There are no overweight kids in DS2's primary class- I don't think there are any in the school. There might be a few overweight kids in DS1's secondary school, but it's definitely not the norm, and he and his friends' pastimes include surfing, hiking and jumping off quays 🙄.
So, there's nobody around us going "Eat, eat, have a treat, a little bit of what you fancy does you good, nothing wrong with being curvy", etc etc. The only time I feel this pressure- basically validating the food noise inside my head- is at Christmas, when I cave in to the national madness, and put so much weight on in 10 days that it takes a month of punitive dieting to undo.
So, I'd say we live in a less intensely obesogenic environment than the rest of the country. Certainly, when tourists from other parts of the UK descend in the summer, I'd say the average BMI of the county increases sharply 😬.
Regarding genetic predisposition: I'm currently dating a thin man....at least he was...🤔. For his whole life, he has been extremely thin/ underweight, due to having little appetite. He just hasn't wanted to eat, and in fact used to envy people who could enjoy a full meal! And his mother is very similar. But he wasn't healthy- he smoked, drank too much, and had very complex mental health issues, and has had an intense desk bound job all his working life, meaning he's never done much exercise.
Nowadays, he's given up smoking and, crucially, is on a new drug regime that has made him more stable- and given him an appetite! It's one of the notorious drugs for weight gain, and suddenly he's enjoying eating like a normal person! He's finding it all very novel, but is also perturbed that a small belly has appeared. He previously would subsist mostly on unhealthy snacks, and I am finding myself in the position of sharing all the knowledge I have accrued over many years experience as a greedy person- stop the snacks! Eat vegetables and protein! Embrace exercise! etc.
But I have found his experience fascinating- it's like a reverse Mounjaro, and I'd love to know how that drug works in stimulating appetite. And it's demonstrated how much appetite- and weight- is dictated by our body chemistry- genetically determined, but also able to be overriden by drugs.