Perhaps you've noticed the recent newspaper ads for something called the "vinegar diet," which promises that you can lose weight without cutting calories or going hungry. The hitch is you have to drink vinegar several times daily. I haven't tried the regimen but I suspect it would sour me even further on dieting. Unless, however, I could substitute that most un-vinegar-like of vinegars, the balsamic variety. Authentic balsamic vinegar, a conspicuous exception to the old adage that you can catch