Before we got Ozempic there was great hope for

https://en.wikipedia.org/wiki/Rimonabant

which blocks the receptor that THC binds to and led to weight loss and further improvements of the “metabolic syndrome” beyond weight loss alone. Unfortunately it caused major depression in some people including suicide.

So looking at it that way it would be no surprise that cannabis causes weight gain and metabolic syndrome and in fact my experience is that if I am using cannabis I get a few kg. I think that is the THC and on top of that if you are smoking you are inhaling small particles that turn your blood into sludge (e.g. your blood is a “complex fluid” with cells in it that can be damaged) and doing damage to your lungs and capillaries and promoting inflammation and all that.