I've had similar ideas for a while. That there's either a blocker of GLP-1 in our modern environment or something that previously produced or triggered production is missing.

I've not found any promising leads, besides maybe something fuzzy about intestinal microbiome. But I've not given up hope of figuring it out.

Especially, I'd note that if a food production company had accidentally added, say a GLP-1 antagonist (without knowing what it was) to their product, they'd just notice sales go up and consider it quite good business.