Metabolism is, well, complex. The hunger regulating mechanism is for obvious reasons extremely primal and the system is shot through multiple redundancies and fail safes to ensure the organism does not accidently starve to death. As such you don’t want to hang your hat on such a minor result.
At the same time. BPA looks exactly like what we would expect the obesity molecule to look it from a macro point of view. Its something that was suddenly everywhere. It works on a key channel. Even without any direct empirical evidence it would a plausible candidate for “metabolic lead.”