Why reducing diets don't work, and why we should stop worrying about it--from responsible proponents of the accept-yourself-as-you-are school. The evidence is mounting, the psychologist authors point out, that letting the body maintain itself at its ""natural weight"" is by far the healthiest nutritional practice. (Though even Miss Americas and Playboy models are getting skinnier, thin is just not right for everyone.) Physiologically, they argue, we operate so as to defend our body weight at a particular level that's right for us individually--an argument reinforced by studies showing that most people have immense difficulting losing or gaining weight beyond a certain level. But not only may it be impossible to achieve a lasting weight loss, it may also be undesirable. The firmly documented benefits of an ""ideal weight"" are few, Polivy and Herman point out (less likelihood of high blood pressure is one of them), while much damage can be done by constant dieting. Aside from the psychological cost (feelings of unworthiness or guilt with each transgression), sticking to a diet interferes with the dieter's ability to interpret the body's signals of hunger and satiety--a vital physiological protective mechanism. Does this mean we can ignore cautions and let our bodies do as they will? Not quite, says Polivy and Herman; but we should assess our individual situations very carefully before deciding to diet, rather than just hopping on the bandwagon. Much the same ground is covered, as ably, in William Bennett and Joel Gurin's The Dieter's Dilemma (1982), though with somewhat different emphases (more on the role of exercise, less on the importance of heeding body signals). But considering the plethora of diet guides and the general addiction to dieting, this re-emphasis of a new point of view is welcome.