Food for thought.

I note that pleasure activates the neurobiological response that fuels addictive behavior ("Food Fix: Neurobiology highlights similarities between obesity and drug addiction,' SN: 9/3/05, p. 155). It has long been a tenet of the 12-step programs that there is no pleasure greater than to use one's talents to help others similarly afflicted. Perhaps we shouldn't discount the neurological effect of that activity. BETSY (LAST NAME WITHHELD)

It's a fact that drug addicts have a deficiency in certain dopamine receptors. However, without determining that such deficiency predates the addiction process, we can't be sure that this represents a cause rather than an effect. It is equally credible that, once addicted, the drug abuser's brain attempts to compensate for the flood of induced dopamine by reducing the number of sensitive receptors. This fits with induced drug tolerance, in which an addict becomes less sensitive to the euphoric effects of a drug over time, requiring increasing doses to achieve equal effect. Perhaps, over time, people for whom food is the euphoriant also require larger doses to achieve satisfaction. DAVID P. VERNON, TUCSON, ARIZ.

Of course, drug-based approaches (however ironic) may help addicts. But it seems like a really interesting question to ask what happens in the brains of the people who choose to change their lifestyles, whether by a 12-step program or some other method. DAVID WINE, SEATTLE, WASH.