Dr. Mayer is a Professor of Nutrition at the Harvard School of Public Health and a syndicated newspaper columnist; here he combines basic dietary theory with puffs of polemic and Q. and A. treatments of a variety of subjects. Sensible exercise and balanced meals are the key--but those now concerned with the safety and quality of American food will not like his casual dismissal of items like the nitrites and nitrates used in meat (a bologna sandwich is O.K.); his boosting of American white bread and arguable reasoning on such matters as ""organic"" foods: ""Organic fertilizers of animal or human origin are conspicuously the most likely to contain gastrointestinal parasites."" One is also deterred by Mayer's casual maneuvering of statistics, e.g., at one point he mentions that a four m.p.h. walk is worth 250 calories if you weigh 150 lbs.; in a nearby table it takes 50 minutes of walking to work off a 51 calorie chocolate chip cookie. Along the way Dr. Mayer offers information on nutritional values of food (although what he means by ""Glucose. . . is the only true 'brain food'"" is anybody's guess), obesity avoidance, diets for young, old, and heart patients, etc., marketing and labeling. Many of his fundamental guidelines are sound but one is distracted not only by the haphazard organization but by the offhand, overly simplistic statements and his paternalistic humor which may sound merely flippant.