Steven, if I am not mistaken the serotonin uptake problems you describe (serotonin/dopamine receptors being overloaded, and the body learning to uptake less as a result) are also used to explain addiction, correct?
This cycle is a physiological explanation for why food can be such a psychological comfort . . . It would be interesting to compare the brain scans of a very obese person eating a candy bar with a heroin addict receiving an injection of methadone (as I highly doubt any research facility would be allowed to use tarballs!).