What's the secret behind the success of the Scarsdale Diet? ""It works,"" says Dr. Tarnower, its modest developer, and you can bet he doesn't get any more precise than that. Written with Samm Sinclair Baker, who collaborated with Dr. (lots-of-liquid) Stillman, this neatly outlines the popular, much-publicized diet, its two-week menus and forbidden fruits, and repeats the important watchwords: two weeks only and no substitutions. Basically, it's a high-protein, low-fat, low-carbohydrates regimen limited to 14 days--a healthy person can,t develop a deficiency in that time--that includes all the usual diet apparatus: behavior modification techniques, retrained palate goals, slightly obsessional restrictions. Tarnower also tucks in some alternatives--a moneysaver variation, featuring less expensive cuts of meat, often marinated; a vegetarian version, which allows potatoes (otherwise prohibited); and a gourmet version, calling for more exotic and often more costly ingredients. Don't expect scientific documentation of results beyond the usual ""I-lost-so-much"" comments, and don't expect head-on answers to key questions: Does the Scarsdale diet overcome the problem of ""fat cells?"" ""Whether or not they have excess 'fat cells,' many obese people have succeeded in taking off their overweight on the diet."" Give it more than a slim chance.