You have to be careful how you define metabolic disorder, do you mean entirely genetic of which there are not many, or do you mean auto-immune of which there are very many. To the point I'd even suggest that it's the dominant factor. Also there are no places in Latin America which has 5% obesity - it's more like 5 to 20%. Really only leaves Sub Saharan Africa, and parts of South East Asia. Additionally Europe is 5-10% so it's not a 1st world 3rd world split as you are presenting.
Anyway, if you are interested in researching check out the field of dysautonomia - there are many good books on the topic. It's an established science but not well known so people are unlikely to come across it by chance.
The main problem is that these conditions are severely underdiagnosed, thankfully people can now access GLP-1As without diagnoses so are no longer reliant on the competence of doctors.
I am comparing modern countries so that relatively a lot of the factors, like access to food, stay the same as the US.
My question is, why does Switzerland, Norway, Sweden, France, Denmark have a <20% obesity rate, and Japan, South Korea have <6%, but the US has 40%+? Certainly this isn't all from metabolic disorders, undiagnosed or not?
You can also perhaps compare data historically. People have never been this overweight, and likewise people have never been eating this many calories. You can a historic chart showing caloric intake and BMI are strongly correlated (both countries with higher intake are higher BMI, and over time, rise in caloric intake is associated with higher BMI) https://www.sciencedirect.com/science/article/pii/S030691922... https://ars.els-cdn.com/content/image/1-s2.0-S03069192220005...
Lastly, metabolic disorders can be caused by being overweight and inactive, so I think the causality is often opposite the direction you're suggesting.
Your logic is scattered and incoherent. You still haven't pinned down your definition of metabolic disorder, as mentioned my definition includes those caused by auto-immune. I explicitly stated that poor quality of food eaten too regularly is causative in many cases, genetics and lifestyle also plays a factor. You're hung up on the number of calories, my position is that is entirely secondary to what those calories are and the cadence of intake. There needs to be a gap in the intake for the natural GLP-1As to take effect. The point of having a mental model is to help make wise choices to optimize an outcome - your model is reductive and far too simplistic and elides many important factors that should be considered. Your position was more tenable in the absence of the data we now have. GLP1-As work, people know it works, and no amount of 'diet and exercise' is the one true path to enlightenment religiosity is going to cause people to unlearn it. I understand the strong desire to blame people for their choices, empathy is painful, and I understand the assumption that there is a price for everything - that nothing comes for free. But that presupposes a prior optimal homeostasis which for a variety of reasons we did not have. Modern diets / lifestyles created a problem that now modern medicine can help with. As a side benefit the medication works for those with my genes where diet and exercise simply wouldn't work. And in my case it's not a modern ailment, people with my genetic profile have had a rough life since before Hippocrates.