No one who brings up Fen Phen seems to grasp how long both that and GLP-1s have been on the market. We're up to 4x Fen Phen's run already (5-years Vs. 20-years). GLP-1 Agonists aren't new, they've just been approved for additional usages.

So why, after 20-years, and millions of people haven't fen-phen-like side effects appeared?