I’m really far behind on clinical literature on the subject (I’m in a different field), but I remember a recent discovery that there were “sweetness” sensors in the gut. I’m not sure if it was speculation or already shown, but the theory is that detection of sweet things in the gut stimulated release of insulin. Since blood glucose doesn’t increase with zero calorie drinks, it can drop blood glucose, increasing hunger.

It’s known that some zero calorie sweeteners we can’t digest, but our gut bacteria can, and it changes them in a negative way.