We have a brain that seeks diversity and foods high in calories or salt. The average diet is equally high in fat, carbs, and salt. This is why ultra-processed foods aren't good for losing weight, as they are optimized for taste.
Pick any food you like, eat only that food for a couple of months, and you'll lose weight like crazy.
High carb and low carb diets work simply because they reduce choice. Except that food producers have caught on to it, and are now producing plenty of junk food that's within any macros parameters you want. The brain also eventually adjusts to the scarcity of some food group or another, it reajusts, and appetite comes back.
Also, compliance for such diets is absolutely terrible, most people putting all the weight back eventually.
There's no escaping the fact that what's making us fat is simply food availability, and that to lose weight we have to eat less somehow, either by strong will, or by medical assistance.
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As for people wishing for food to be more expensive, such that they or others can lose weight ... OMG. I guess starving the poor is one way to solve obesity or overpopulation. The silliness of degrowth policies applied to our food supply.
I mean - I think I understand the motivation behind that but
I am pretty convinced that the value of "low-carb" / "no-carb" diets has less to do with the impact of carbs (after all, wheat literally was the symbol of European civilization for a really long time) and more to do with how they're used as cheap caloric filler (looking at you, Panda Express). Pretty much a "get what you pay for" kind of situation, in my eyes - so maybe spending that much on food isn't as bad as was thought.
also, on the gripping hand, looks at cost of housing - so maybe if it's not one thing it's another.