Why is diabetes spreading around the world?

The unfortunate normalisation of sugary and industrial foods spreading rapidly across the world is causing this. Crap food is relativelly cheaper, widely avaliable and easier to consume, doesn't require much preparation so people tend to make these food choices, which causes, among other things, problems like diabetes in first world countries and now in developing countries especially in Asia and South America where this modern lifestyle is being implemented at a very fast rate. Add to this the increasingly sedentary lifestyle that people have, especially in cities, and you will see obesity and diabetes.

Cities are actually less sedentary. Cities have walkable destinations and public transit (which requires walking to). Living in the suburbs or rural areas, you rely on a car for every trip.

I've lived in big cities, suburbs, and a rural area. You see so many more people walking and biking in the cities.

Try removing sugar from your diet, like sucrose sugar. It is frighteningly hard unless you're cooking everything you eat yourself.

I've had times where I start liking something a lot which I normally wouldn't suspect of having lots of sugar to realise "wait a minute, I like this because they've added lots of sugar don't I!?" ... and I check and yea there's way too much.

It's a problem.

People are fat. Thats why.

All of the food contains added sugar. All of the food that’s easiest to get (y’know, since nobody has time from being worked to death) is cheapest. The problem is much much deeper than ‘lol fat’.
- I don't think I agree with this "nobody has time" thing. Most people don't get that excuse, you can usually make time, most people just choose not to. Do you make time to shower and brush your teeth?
  
  I understand that there are food deserts and some people legitimately work multiple jobs and have kids and that fast food or microwavable dinners and generally unhealthy foods are quick and convenient and affordable but cooking your food doesn't take that much time and not drinking soda frequently takes no time.
  
  Also it's not like veggies and lean meats like chicken are expensive for most people in the US. You can genuinely fill up your basket with lots of leafy greens, veggies, mushrooms and some animal protein for significantly cheaper than with junk food and microwavable dinners, hot pockets, deli meats and cheeses and bread. Unless you live in Alaska maybe.
  
  Not being dismissive of peoples' struggles, a ton of us are being overworked for less money than we're worth, but if you need to you'll make time, you figure it out. Yeah there's sugar in everything processed, cool, you have affordable options that admittedly take a bit of effort to prepare and don't taste as good, but we can eat those and we can eat less. Overeating, constant junk snacking and portion size is also a huge issue in our culture.

Cheap food is typically unhealthy and full of sugar.

People be fat

For a non meme answer. my bet would be on endocrine disruption of the thyroid, by pollutants.
Along with a change in feeding habits in former third world population (sudden access to an abundance of sugar when you're not genetically ready for it).
And maybe compound it with unhealthy lifestyles (increasing sedentary lifestyles).

What do you mean by "not genetically ready for it"? People in third world countries don't have significantly different genetics to those in first world countries, and people in first world countries haven't evolved since the introduction of McDonald's
- haven't evolved
  I'm not so sure. We've been eating like shit since way before mcdonalds, and natural selection gonna naturally select.
  
  It may be coincidental, but there's an abnormally high (higher than western population) prevalence of diabetes in people transitioning to a western lifestyle.

People are too lazy to cook for themselves.

Or just too busy.
- Especially for people living in poverty/low income. Most of the tools that make cooking more efficient can be really cost prohibitive, so people working long hours/multiple jobs don’t have time to make every meal themselves and who don’t have access to things like Instapots or even just quality ovens that heat quickly and evenly, etc etc. factor in food deserts and many people just don’t have realistic alternatives to quick, cheap, sugar-laden foods.
  
  And some people just don’t even know how to realy cook. My husband grew up in severe poverty with very neglectful parents who would literally do things like hand him a box of snack cakes when he was 9 years old and that was his “dinner.”
  
  He has no idea how to do most things in the kitchen (and to be clear he does probably 90% of the cleaning in our home, it’s definitely not weaponized incompetence due to laziness). I grew up cooking with my parents and being involved with it as soon as I was old enough to stir the batter for the pancakes. So much of it is so second nature to me that I forget there are a lot of nuances to cooking well that I take for granted.
  
  Eg, We watched the episode of Schitt’s Creek where Moira and David can’t figure out how to “fold in” the cheese and my husband asked me what it meant because he had never heard of that before, either. Knowing certain techniques, knowing how to use different tools, having basic recipes memorized, knowing what kind of spices go together for what kind of dish, if you don’t already know these kinds of things it’s time consuming to have to look it all up and learn. Overworked people don’t have that luxury of time and access to good learning resources.
Or, perhaps, they have no time to do so.
- No energy to do so because they're overworked and underappreciated.

Dietary fiber. No seriously. 95% of Americans don't get enough, which leads to an unhealthy guy, which leads to inflammation and gut-brain axis disturbance.

Processed food is processed to remove fiber. Americans that eat a higher percentage of fast/processed food (ie. The poorer ones) get less fiber and more sugar, which is a bad combo for gut health.

Ever seen what other apes eat? Leaves, flowers, seeds, shoots, roots, insects, fruit and occasionally meat. In other words, they eat fiber and lots of it.

Cocacola and Nestle Co.

Is it spreading, or is this like "why do so many women suddenly get autism" misconception?

Not the same misconception, though it's a poor choice of wording.

Type II diabetes cases are actually increasing around the world, due to factors another comment summarizes very well, but it's not obviously "spreading" like a contagious disease.

It's not an issue of doctors starting to diagnose something that always existed but went undiagnosed due to ignorance/bias like the case with autistic women.

It comes down to diet.

Two things: eating a plant based diet, and fasting.

Dr. Neal Barnard: https://youtu.be/tAiXvrIMIIE

Dr. Jason Fung: https://youtu.be/mAwgdX5VxGc

Dr. Michael Greger: https://youtu.be/UTxLHqeXZNQ

Dr. John Scharffenberg: https://youtu.be/iddFlIcxQi4

Dr. WIll Bulsiewicz: https://youtu.be/65sxIFq0F0g
https://youtu.be/EABZqi3HtRM

Ultra-processed foods.

Can this be answered via Parks and Rec clip? https://youtu.be/Ish8NBunrQU

Is this due to factors beyond the control of people? ie. genes?

Gene predispositions likely haven't increased, though perhaps the proportion of people having children with gene predisopositions have.

Ultimately, it's due to people with lifestyles that our bodies are not designed for and not moving/exercising enough, with a small amount due to family history/genetic reasons.

I’m pretty sure it’s primarily changing diets that include way more carbohydrates, combined with lifestyle changes like increasing use of automobiles. I have Type 1 (the far less common autoimmune version, which is really about the opposite of type 2 with some overlapping effects) and the amount of carbs in typical American meals blows me away. Type 2 is essentially insulin tolerance (called resistance), like one gets to psychoactive drugs with repeated intake. People eat such an insane amount of carbs (not just sugar, but rice, potatoes, wheat, corn, tapioca) that their bodies have to release a flood of insulin to try to maintain glucose levels… and after a while it just stops working as well. The thing is Type 2 can be managed pretty well simply with low carb or keto diets but most people aren’t willing to make that change to their food intake.