A psychobiologist with a keen interest in weight control, Atrens carefully and with humor explains how moderation in diet and exercise is more healthy and less expensive than compulsive programs. He contends that being fat does not necessarily mean being unhealthy, weight loss is not possible or desirable for most people, diets don't work, and exercise is not a good way to lose weight. The overweight can improve their health by not smoking, participating in reasonable and regular exercise, increasing carbohydrate intake, and decreasing saturated fat. Massive obesity, diabetes, cardiovascular disease, and high cholesterol are the only reasons for which fat is a real health concern. Too sensible to be a best seller, but libraries should purchase. Anne Washburn, Smith Helms Mulliss & Moore Lib., Greensboro, N.C.