After reading a grim catalogue of the signs of age and decrepitude--heart disease, cancer, arthritis, etc.--we are told, ""You are slowing down. This diet can do something about that."" So Pritikin (Live Longer Now) begins his la-test sally into the health diet field. His program consists of a diet low in protein, fat, and salt, and high in starch, fiber, and exercise (walking or jogging). He gives us a convincing hard-sell explanation of the evils of sugars, honey, cream, eggs, caffeine, and ketosis, and sings the praises of carbohydrates (""the best food you can eat""), root vegetables, breads, grains (whole, if possible), fruits, and so on. He prescribes diets of varying severity divided into menus and recipes. The result, he says modestly, is ""probably the most feasible method of attaining an extra twenty to thirty years of vigorous life."" Case histories and testimonials proffer details of lost weight, refound vigor, and mended cardiovascular systems. A book whose basic principles have some merit, though it suffers from the hyper-salesmanship endemic to the diet field.