TL;DR: This is a long one, you may want to skip

You can look back and watch the decay of sugar too.

Sugar not great for you from the jump, but there were "studies" that showed it was much worse for you than it is, and then corn syrup came to the mass market and the rest is history.

I know I'm not the only one who remembers popsicle commercials in the 90s/possibly early 2000s using slogans like "It's better for you than sugar, because it comes from corn! A vegetable!" because high fructose corn syrup was starting to replace sugar.

This progression has continued further, leading to a using it many different candies and drinks not just for the sweetness, but the texture, the "creamy smoothness" of the syrup.

What this did in practice was increase the amount of carbohydrates in our foods, far surpassing the amount of natural (and yes, even refined) sugars that we used to put into our foods as flavor enhancers, and now entire generations have grown up on this.

This has desensitized our sweet receptors so that we engorge ourselves on carbs to achieve the sweet cravings we have.

This contributes to insulin sensitivity problems (pre- and diabetes) and jacks up the inflammation in our bodies, leading to more aches and pains and developmental issues that we didn't have before.

It's also a multifaceted problem, because insulin releases make us hungrier, like salt makes us thirstier. This can drive people to consume even thousands of calories per day from drinks, and also consumption of thousands more calorically and carb dense foods.

Most people who don't moderate their carb consumption (e.g. too much alcohol, too many carb heavy foods like breads, too much pop) end up feeling lethargic, tired or sore and figure "hey, let's just go to Taco Bell or McDonald's"

Which are calorically dense, often accompanied by more pop, and incredibly dense in carbs and salt..which makes them crave more food and drink and suddenly there is an obesity problem.

A lot of our problems can be traced back to junk science like corn syrup being healthier than sugar, and those junk sciences reinforce bad culture like the overly body positive people who will call you fat phobic if you even suggest that YOU YOURSELF want to drop weight to be healthier or fit into better clothes.

We need to be discerning with our science more. The experts are paid by people with an agenda.

Diets can be improved. We can learn new things. But we also need to look back and look at present and acknowledge that there is a problem and that problem is not necessarily just related to the availability of food, but rather what is added in our food to make us crave more.

Saturated fats vilified in favor of brominated, unsaturated, mono- oils, so many additives to many oils, etc.

Cheese has been vilified a lot too, as a contributing factor for high blood pressure or cholesterol when cheese focused food cultures are thinner than our obese western cultures.

Salt has been overly pointed at for blood pressure related heart failure, when a fairly sedentary, salt focused culture is known for their long lives and meme-worthy youthful looks and have pretty normal blood pressure -- referencing Asian cultures here, mostly Japan, which is a fish focused culture that consumes a lot of salty foods like ramen (salty broths) and seaweed (salty due to the ocean) and fish which are already salty too.

We have years of vilifying eggs for raising cholesterol too, only to be told when we actually look into it that there's a difference between LDL and HDL cholesterol, and you don't want to "lower" so much as ensure that your HDL is higher and your LDL is as low as possible, so the cholesterol won't stick to each other or your arterial walls and create a blockage.

We really need to take a look back at other healthier cultures and our own older cultures and start tearing down junk science that does not stand up to scrutiny or the test of time.

We need to stop blindly "trusting the experts", and start making more room for alternative and independent studies, stop blindly trusting the incestuous "peer reviewing" processes as the driving force of our health guidance.

Simultaneously, we need to tackle a few problems at the same time:

What is being put in our food and soil

Educating people better on what it means to eat responsibly, the give and take of food consumption vs exercise; e.g. maybe if they have a sedentary day or week have less in the way of snacking, maybe don't have that gallon of ice cream, maybe don't eat McDonald's that day or eat something a little smaller.

We also need to tackle the cultural problems. We need to differentiate and explicitly separate being positive about yourself and happy with who you are and normalizing of land whale culture.

This doesn't take directly fat shaming someone, but harsh social response needs to come down on people who are directly promoting getting and being fat. That there is a community of people influencing our laws and social culture focused on a hierarchy of how fat they are is insane lunacy. They are changing how doctors interact with their patients, to avoid hurting feelings. It's awful.

People need to be told by someone that they could stand to lose 10, 20, ...300 pounds. This is directly related to the job of a physician and they are being shamed if they do. We need to harshly and socially come down on that.