It is complex. Taxing 'unhealthy' foods is one measure but there's other things that can be done,control of advertising etc.
I would like to see more emphasis on food in school. We had a Home Ec. teacher leave last year and it was a nightmare trying to replace her, pupils spent months without cooking. The impression that I got from others was that this wasn't a surprise and that there weren't enough Home Ec teachers being trained.
Another thing is school meals. I left a school that, I suspect, was highly unusual but shows what can be done. The meals were so good that pupils stayed in and sat down and really enjoyed them. I'll try and post a photo at some point. Where I am now, none of the choices are inspiring, lots of kids leave school at lunchtime, local businesses do well but I'm not sure it's getting young people into healthy eating habits. Add in the expectation fuelled by Deliveroo adverts that takeaways are a regular occurrence and we've got a problem.