The weight that's healthiest for you may be heavier than you think. Use our easy formula to find out.

Yvette is obsessed with numbers. Not all of them, mind you -- just 30 and 8. Thirty is the number of pounds she needs to lose in order to reach the "ideal" weight for someone her age and height (according to an official-looking chart in a magazine she flipped through at Nefertiti's Clip 'n' Curl). And 8 is the size of the jeans she figures she'll be able to fit into once she drops the 30 pounds.

Now, as obsessions go, you might argue that Yvette's is fairly harmless. After all, she's not losing sleep over some no-account pretty boy or maxing out her charge card on another "must have" outfit. But harmless it's not. She has dieted nonstop for more than a decade, with little long-term success. Oh sure, she's lost weight. Once, she even dropped close to 15 pounds in three hellish weeks prior to her high-school reunion. Within a month, however, she had regained every pound, and lost a good deal of her hard-won self-confidence to boot.

Unfortunately, Yvette's case isn't unusual. Experts estimate that more than 50 percent of all diet-program participants regain any weight they lose within two years--in part because their goals for weight loss tend to be highly unrealistic.

Time to Get Real

For years, doctors and nutritionists determined ideal weights for their patients by consulting the height-weight charts published by the Metropolitan Life Insurance Company, charts that most experts now agree are misleading because they don't account for a woman's body type or metabolism.

In reality, those charts mean about as much as the ones on the backs of panty-hose packages--they're guidelines, not gospel. "There's no such thing as an ideal body weight unless you're talking about the weight at which you feel most comfortable," says Judith S. Stern, Sc.D., professor of nutrition and internal medicine at the University of California, Davis. "Experts now talk about healthy body weight, or the weight at which your risk for disease--such as high blood pressure, which is associated with excess weight--decreases. Surprisingly, the weight at which you're healthiest may be heavier than you might expect."

Exactly how much meat should you have on them bones? "Your optimal weight is the weight at which you'll end up after making certain lifestyle changes, such as reducing your fat intake and engaging in regular aerobic exercise," advises John P. Foreyt, Ph.D., director of the Nutrition Research Clinic at Baylor College of Medicine in Houston and coauthor of Living Without Dieting.

Foreyt's answer sounds reasonable, but what's the real skinny? Most women want a three-digit number to shoot for, so when pressed, Foreyt recommends the following formula: Your healthy weight is the lowest weight you've been able to maintain for a year as an adult while exercising regularly and eating healthfully. For instance, if you hovered around 140 pounds for a year back when you were 23, and you were active and ate healthily at that weight, your goal weight should be no lower than 140 pounds. If you've never exercised consistently or maintained a low-fat diet (one that derives no more than 25 percent of calories from fat), start to do so. And the weight at which you'll arrive and remain, according to Foreyt, will be your healthy body weight.

Hitting the Mark

Once you've come up with the body weight that's best for you, you have to map out a workable plan for achieving your goal. George Blackburn, M.D., Ph.D.--chief of surgical nutrition at New England Deaconess Hospital in Boston and one of the nation's foremost authorities on weight concerns--advises that, for starters, you aim to lose no more than 10 percent of your body weight at the rate of no more than a pound a week. Only after maintaining that 10 percent loss for six months and checking with your physician should you attempt to take off another 10 percent. Here's the easy way you can get started now--and stick with it:

Eat heartily. It's ironic but true: Severely limiting the amount of food you eat can actually cause you to gain weight. How? By slowing your metabolism, or the rate at which your body burns calories while at rest. So resist the urge to fast, and eat lots of healthful, low-fat foods such as pasta, potatoes, fruits, and vegetables.

Eat early and often. Most women in this country who have weight problems consume 75 percent of their calories after 5 P.M., when their bodies need them the least. "If you want to lose weight, you should eat the bulk of your calories earlier in the day. Using more of those calories as energy to race through the day leaves fewer to be stored as fat, " explains Pat Harper, M.S., R.D., a nutrition consultant in Pittsburgh and a spokesperson for the American Dietetic Association.

Harper's advice: Eat small meals at more frequent intervals throughout the day so that you never consume more calories than your body can burn in a few hours. Indulge in a substantial breakfast--a bowl of hearty, low-fat cereal topped with fruit, for instance--to rev up metabolism and begin your day with a satisfied stomach. Then munch on relatively small meals or snacks of low-fat, healthful foods every three or four hours to curb your appetite, instead of starving yourself all day and then gorging yourself all evening.

Indulge in your favorites. One surefire way to blow a diet plan is to stop eating your favorite foods. "The key to losing weight is cutting fat and calories where it hurts the least," says Connie Diekman, R.D., also a spokesperson for the American Dietetic Association. "If you love pizza, it's not the food to sacrifice." Doing so will only increase your desire for it.

Simply eat smaller portions less often and trim fat from your diet where you won't miss it so much. For instance, if you spread your morning toast with fat-free fruit preserves instead of butter, you' ll save up to 50 fat calories that day. In fact, you'll save 350 calories in just one week with this simple substitution and 3,500 (the equivalent of a pound of body weight) in ten short weeks.

If you decide to eliminate fatty foods such as cream, butter, oily salad dressings, and red meats from your diet, do so slowly--over about three months--to give your taste buds time to adapt. Research conducted at the Monell Chemical Senses Center in Philadelphia reveals that people who are put on a reduced-fat diet for three months and weaned from fatty condiments such as salad dressings, mayonnaise, and margarine lose much of their taste for those foods.

Exercise comfortably. Walking at a pace that lets you breathe deeply and rhythmically without gasping is ideal for burning fat, although any activity that uses major muscle groups is excellent. Good examples include cycling, swimming, running, and aerobics.

"You don't get any points for getting soaked with sweat," says Blackburn. "Just keep your engine running slightly above idling and rack up the minutes." Gradually work up to exercising for 45 minutes, without stopping, at least three times a week.

Get pumped. Muscle requires more calories than fat does to sustain itself, so the more muscular you are, the speedier your metabolism. And a vigorous metabolism is the key to losing weight and keeping it off. In fact, you'll burn 30 to 50 more calories a day for every pound of additional muscle you build, explains Wayne Westcott, Ph.D., a strength-training consultant for the national YMCA.

If you want to build lean muscle fast, Westcott suggests that you perform exercises that work the body's largest muscle groups, such as those in the chest and shoulders, abdomen and back, and legs and buttocks. Aim for one or two sets of 8 to 12 repetitions of each exercise. If you're just beginning, though, don't knock yourself out. Allow your body time to adjust by lifting light (two-to four-pound) weights. As you become more comfortable with the exercises, you can begin to push yourself a little harder by increasing the weight and the repetitions as your strength and fitness improve. Once you are strength-training strenuously for a half hour, three times a week, you may build as much as a pound of muscle every two to three weeks.

Reward yourself with acceptance. There's nothing revolutionary about the simple weight-loss program described here, except that it works. Like a charm. Follow it and you will achieve your optimal body weight--in other words, a healthy weight that looks terrific and is right for you. Congratulate yourself and accept your trimmer body as it is, even if you still can't grease yourself into size-8 jeans. Just remember that looking and feeling good isn't only about size; it's also about self-acceptance and perspective. Make sure you have both.