The way to lose weight is to eat less of whatever it is that you are eating.

This is the sole piece of useful information contained in any diet book, give or take a recipe for Tangy Zippy Zesty No-Cal salad dressing that wouldn't fool a grasshopper in a famine. So why do the frequent restatements of this dismal fact by doctors, nutritionists, psychologists and born-again skinnies weigh in at an average of 200 pages?

Because, as Chris Chase points out in "The Great American Waistline," we are a nation that regards fattening foods and thin bodies with equal enthusiasm, as the two great salacious treats in life.

To scorn "gourmet" food is unsophisticated, to scorn "junk" food is un-American, and to hold up your bathing suit pants with anything more than two protruding hip bones is unhealthy, not to mention disgusting.

Hence the diet book. It must be padded, because anyone who could swallow that bitter pill without sugar coating wouldn't be in the predicament in which all diet-book readers happen to be.

There are only so many ways this can be done, but some books run through the entire formula -- preying on health fears, jeering at appearances, teasing about foibles, discussing motivations, offering rigid menus for balanced or unbalanced meals, extoling some foods and condemning others -- while others concentrate on a particular aspect.

A favorite opening is the explanation of why you are overweight (guess), the exposure of the habits of greed, and the announcement that all other diets -- always grouped under the generic term fads -- are ineffective, dangerous and no fun. This is a favorite litany of diet fans, because, like a horoscope that says your true worth has not yet been recognized, it seems to apply uncannily to the individual reader.

The Chase book consists entirely of this material, subdivided into "Putting It On" and "Taking It Off." Written in puns, of the order of "fear of frying," "prima boilerina," and "chacun a son goo," it gives a superficial history -- not that one would want a deep one -- of food and diet fashions and anecdotes about food establishment celebrities.

But while it has the unmistakable tone of being written for a ready market (after Chase wrote her funny autobiography, for which there could have been no advance demand, she wrote forced ones for which there presumably was, for Betty Ford and Rosaling Russell), it doesn't offer much interest to those who are not hopelessly addicted to rich food, or any hope to those who are.

It may be candid to stop after identifying the problem, but anyone who makes the commitment of buying a diet book expects to be lulled, scared, ridiculed or fooled into believing that one may have both good food and a good figure.

The usual next step is to advise you to check with a doctor, and then to explain what the doctor has been pushing all along, which is basic nutrition and steady good eating habits. Many diehards skip this part because they know what is coming -- boring food charts and lectures about the importance of breakfast -- and don't want to waste valuable calories on sensible foods when they could save them to splurge on goodies.

Two weeks of privation sound more bearable to most people than a life-time of being sensible, and if the short-term diet plans are always followed by advice about a controlled future -- well, you'll worry about that part when you're thin, two weeks from now. The new Pritikin book has an exact menu plan, after when you will come to believe that you can satisfy a craving for sweets with a raw vegetable stick; and the "Beverly Hills Medical Diet" has one that will remove from your life the stress attributed to guilt from overeating. The other book, just out with nearly the same title, "The Beverly Hills Diet," advocates something called "conscious combining" to control eating.

All three books attack the previously fashionable high-protein diets, and offer plans with limited amounts of certain healthful foods, for which they supply deceptively sexy names and disillusioning recipes.

Another fixture of the genre is the explanation of why you overeat (to celebrate happiness or to compensate for unhappiness; because you are in the habit of cleaning platters at meal-times or because you use food as a pastime -- or most likely, all four at once), with the suggestion that you stop eating when you have satisfied your hunger.

The "Marshall Plan" concentrates on this aspect, recommending over-whelming yourself with treats until you can't take it any longer and recognize a stopping point.

"How do you decide when that point is?" it asks with some poignance. "When you keel over? When you rupture your stomach? When your eyes roll up in their sockets?"

The book promises to establish earlier warning signs, but in the meantime, these will continue to serve most food lovers -- who have learned to reach, after these warnings, for a good stiff diet book.