Japan is probably evidence that the surrounding food culture matters at least as much as the existence of UPFs. You can sell plenty of processed food without getting the same outcome if portion sizes, eating habits, school meals, and daily activity are different. The marijuana comparison feels like a non sequitur, though.

I don't think marijuana use is unrelated. From the NIH in 2024:

> Among adults 19 to 30 years old, approximately 42% reported cannabis use in the past year, 29% in the past month, and 10% daily use (use on 20 or more occasions in the past 30 days). Among adults 35 to 50, reports of use reached 29%, 19%, and 8%, respectively.

https://nida.nih.gov/news-events/news-releases/2024/08/canna...

Those numbers are huge, in absolute terms. Marijuana provably results in higher rates of obesity by simulating appetite in multiple different ways.

In my own experience, marijuana use directly correlated with bodyweight. Even relatively little marijuana resulted in serious cravings, often late in the evening. I don't think you need a study to validate this, it's an extremely widely understood effect.

When you have millions of people consuming an appetite enhancer, it's almost crazy to suggest that it doesn't play a significant role in UPF consumption or health in general.