Yes, there are multipacks of everything now in superarkets, whereas when I was a kid you might go and spend your pocket money on a chocolate bar once a week at the local newsagent as they weren't always available to the same extent in supermarkets as they are now. Sharing bags of crisps are another problem. It's far too easy to eat way more than one person's portion once a bag of those is open andd there aren't multiple people sharing.
The multiplex cinemas arriving in the UK also have contributed. Really pushing the food element of going to the cinema with huge portions of popcorn with loads of calories. It just wasn't like that in the 80s when I'd go most weeks to my local town's cinema (for very cheap entrance too).
Also when I was a kid in the late 70s it was only kids who ate ice cream regularly, often from the ice cream man.. Adults would only have an ice cream cone on a day out. Then the likes of Haagen Dasz arrived, pushing ice cream for adults as a "you're worth it" kind of decadent thing, always paired up with ordinary home activities like watching telly.
All you can eat buffets weren't really a thing years ago. Neither were all inclusives where people feel they have to get their money's worth in both food and drink.
Super sizing has been a problem for years now. It's changed the UK's health for the worse. It's pushed as another "you're worth it" kind of thing. And who wants to think that they AREN'T worth it - it's an easy win for the likes of McDonalds.
Some motorway services are crap - not much choice between the likes of KFC and Maccies. Some are starting to improve and offer healthier types of fast food. But a lot of people see the logos and make a beeline straight for the Big Mac. I mean, you have to eat when you're on a long journey. That's when food IS just fuel. But often you're a captive audience at a motorway services and having junk food thrust in your face as the quickest solution is a surefire way for a nation to get
I did a Tesco shop yesterday. There was so much processed and packaged stuff. More and more of it than there ever used to be. Aisle up on aisle of biscuits, snacks, crisps.