I got diagnosed with type 2 diabetes two years ago. I switched to a super low carb diet (30g per day). Contrast that with a 16oz Mt Dew, which has 77g. Or a bowl of cereal at 36g plus whatever is in the milk.

I ate all kinds of protiens and fats - cheese, meats, fish, veggies just to quell the hunger. I lost about 58 pounds in a year. Most of what I lost was fat. Two years later, I'm still doing a very low carb, but keep it under 50g per day. My weight has stayed ±3 pounds. I'm pretty convinced it's the super-high carb load everyone is eating three times per day.

I am inclined to put that the other way around.

The ultimate cause is consuming too much, the proximate causes are various elements of modern culture (i.e. Bigger serving sizes, more readily available snacks, alcohol consumption, etc).

If it wasn't synthetic we wouldn't see animals growing fat from eating leftover food.

I think sugars and processed food increase hunger rather than reducing it.

There are a few other variables that could play a role.

(1) Share of physical labor jobs vs office jobs

(2) Increased hormone and pesticide use in agriculture (dropping worldwide sperm counts is an underreported story, might or might not be related)

(2A) Less nutritional content in food - has gone down 60% since 1940s according to some studies; likely from over-farming. Need to eat more to get the same nutrients.

(3) Food deserts (related to (1)) - where healthy food options are rare

(4) Less general socialization (internet makes it less necessary to go outside, etc)