Another run-through of exercise, nutrition, and weight control principles? Yes, but possibly a solid pacer. Two exercise physiologists and a professional writer draw on that ubiquitious body of knowledge concerning pulse rate and protein-fat-carbohydrate ratios to help readers evaluate their needs and design their own programs. Some now-standard inclusions appear--how to lose fat rather than muscle tissue or compute your maximum heart rate--along with some inside stuff on professional training techniques (Katch is a U.S. Olympic and N.Y. Jets consultant). Properly emphasized: the need for medical clearance, the importance of warm-up and cool-down exercises (even for walkers), the advantages of liquid meals (for athletes only, before competitions). A reliable, nicely unembellished handbook for the popular fitness/fatness shelf.