waist watchers; One promises to block fat, another claims to control your appetite-Rebecca Johnson reports on the next generation of diet drugs.

Byline: Rebecca Johnson

The drug has no official name, it hasn't yet been approved by the FDA, and it won't be available for months, but already rimonabant (its generic name) has been a plot point on the television show Boston Legal. Every major media outlet from The New York Times to NPR has covered the drug (which has also been called Acomplia). Most of those stories have, at one point, used the word miracle in their description, albeit occasionally in quotation marks. Two unofficial Web sites are devoted to constant updates on its journey toward FDA approval. One of them, AcompliaReport.com, has registered as many as 70,000 visitors in one day. (The drugmaker, Sanofi-Aventis, tried unsuccessfully to shut it down.)

What's all the fuss? Diet drugs are nothing new. Just this winter the FDA moved one step closer to approving a low-dose version of orlistat (now sold by prescription under the brand name Xenical), which would be available over the counter (new name: Alli). The drug blocks the absorption of fat in the gastrointestinal tract and has earned the nickname "oily scat" because of an unfortunate side effect in the bowel department. And who can forget the fen-phen fiasco of only a few years ago? "You can't compare the two," sputtered Doug Greene, M.D., vice president of regulatory development for Sanofi-Aventis, when I brought up that debacle. "It's not even apples and oranges . . . it's grapefruits and peas."

Rimonabant is a grapefruit because it is the first in a new class of drugs to block a pleasure receptor in the brain, the neurotransmitter endocannabinoid, so named because cannabis, a.k.a. marijuana, activates the same receptor. Remember how smoking a joint in college would send you to the freezer for a pint of Hffiagen-Dazs? That was your endogenous cannabinoid system (EC, for short) working overtime. Overweight people seem to have an imbalance in their EC systems, which causes them to overeat or, more likely, feel less full when they do eat. Rimonabant appears to readjust the body's appetite-control mechanism. (Studies also show it curbs nicotine cravings.)

While the hype so far surrounding rimonabant centers on weight ...