WEIGHT, SEX, AND MARRIAGE A Delicate Balance By Richard B. Stuart and Barbara Jacobson Norton. 189 pp. $15.95

If ever a book confirmed that fat is indeed a feminist issue, it's this one. As a typical how-to book about women and obesity, it offers explanations of why so many American women have so much trouble losing weight, as well as sensible solutions to weight-related dilemmas. But the portrait that emerges in the book's case studies goes further than that. It is a reminder of what happens when women define themselves as objects of men's desires, or try to conform to standard images of the "ideal woman."

"Weight, Sex, and Marriage" begins with an account of authors Richard B. Stuart and Barbara Jacobson's efforts to help overweight women reduce. Stuart, former psychological director of Weight Watchers International Inc., is a marriage counselor, and Jacobson is a doctoral candidate in counseling psychology. Over the years, the authors were puzzled by many of their clients' responses to weight loss. Rather than rejoice in their accomplishments, they often became so depressed they immediately regained the pounds they had shed. To understand this intriguing phenomenon, the authors considered several questions -- why do women overeat, what roles does fat play in marriage for both wife and husband, what options does an overweight woman have, how can a woman get ready to lose weight, what dieting plan is best, and how can a husband really help his wife reduce?

The answers to the first question are rather obvious. It's no surprise that women, as well as men, eat when they're bored. Nor is it a surprise that women who get little support or affection often search for substitutes on supermarket shelves.

The book becomes far more interesting and insightful when Stuart and Jacobson begin to discuss how a woman's relationship with her mate or with other men influences her ability to reduce. In a chapter titled "The Many Uses of Fat in Marriage," the authors contend that women use fat to protect themselves from extramarital affairs and to keep their husbands at a distance sexually, to prevent eruptions of anger and to fend off the fear of failure. No wonder then that so many obese women are caught in the cycle of gaining weight, dieting and then gaining it once more. For when they reduce, life becomes more complicated. They're suddenly attractive to their husbands and to other men; they can't simply swallow their anger along with a hot fudge sundae; and they can no longer avoid life's challenges because "no one expects a fat person to succeed."

What is even more disturbing is that many husbands also benefit from their wives' weight problems and thus exploit their obesity. A man whose wife is 50 or 100 pounds overweight doesn't have to deal with feelings of jealousy. No other man would be likely to desire her. Similarly, if a husband has a problem with weight, drinking, smoking, gambling or sex, his overweight wife's self-hatred is useful. A woman who feels she's lucky to have a man -- any man -- will hardly deal aggressively with her husband's bad habits.

On the other hand, a woman who loses weight may pose a real threat to an insecure or troubled husband. "The insecure, passive, fat person of the past often bears no relationship to the confident, active, thin person of the present," the authors report. "And the man that the fat woman chooses to marry may bear no resemblance to the man the thin woman desires." That's why so many husbands suddenly become aggressive advocates of fat the moment their wives lose weight. Since the best way to make sure their wives never reduce is to nag them constantly about their weight, some husbands sabotage their spouses' diets by nagging them unmercifully. Others refuse to eat healthy food along with their wives, or to pay for exercise classes. Still others keep insisting that no matter how much weight their wives have lost, they're still not thin enough. And finally, a minority resort to physical abuse to force their wives to retreat back to the fridge.

Unfortunately, many obese women -- like other emotionally and physically abused women -- have so little sense of self that they prefer to stay fat rather than challenge this response. Instead of insisting that their husbands change, they decide dieting is too much trouble and begin eating again.

The authors argue that obese women must resolve their psychological problems first, recognizing that weight loss will not necessarily secure conjugal bliss. Then, when a woman is ready to weigh the costs of dieting against its benefits, she can follow a phased program of weight loss that will result from the kind of highly personalized dieting regimen the authors recommend.

For any obese or overweight woman, "Weight, Sex, and Marriage" presents useful information and a great deal of hope. In spite of its prudently optimistic message, however, there's more to maintaining the delicate balance of which Stuart and Jacobson speak than self-analysis and confronting the "fattening husband." The real obstacle American women face is a "fattening culture" that does everything possible to discourage a rational relationship between food and the female body. American women are constantly assaulted by images of female beauty that are so thin they border on the anorexic, seduced by an endless series of ridiculous crash diets and pummeled by exercise programs whose implicit message is that no number of pushups or laps will ever be enough. Consequently many women secretly hate their bodies and develop a neurotic attitude to food and the very act of eating. Until these images of women, food and exercise change, many women will probably be condemned to the excesses -- either anorexia, bulimia or obesity -- that have become so prevalent in our society. The reviewer is the author of "Off Balance: The Real World of Ballet."