Education is ultimately the key (having worked on several projects from the EU alongside the WHO etc focused on tackling the current health crisis).
So many people don't know anything about food, calories, what is healthy and what is not... heck, a lot of people who think they do don't either! And when people are educated they generally make better choices.
Food education and cooking classes should really be embedded in every school.
Still... there are serious issues once poverty rears its head in relation to being actually able to provide a healthy diet while also getting a calorie intake that will actually fuel you. Education and some good cooking skills can help that... BUT at the same time? You then have time constraints that come into view. So many families NEED to have both parents working (or the sole parent working) and taking 1 hour to prepare dinner is sometimes not an option even if you can.
And ofc food prices over the last few years have got ridiculous world-wide.
Even as someone who had a multiple year, free, education on an Olympic programme on diet etc and has cooked since I was maybe ~11 years old? And cooks probably ~680 of my 730 meals a year? And has a pretty good salary?
Some days I get ingredients for something that really should be semi-inexpensive and healthy, and just balk at the fact that unless have things in stock already it can be cheaper to go and get a takeaway!
And circling back... then? If a child has a poor diet by the time they hit teenage years (or even earlier in some studies)? Well bodies do adapt and store more fat etc... and then it is harder as an adult to be "healthier". Which is not impossible to overcome ofc, and many do, but makes things harder through really no fault of their own, but their parents choices and education.
It is a multi-faceted issue.