It's OK to be heavy if you're healthy. It's better to be shaped like a pear than an apple. And if you're trying to lose weight, don't lose more than a pound a week.

Those are some of the messages from the new U.S. Dietary Guidelines, a list of general advice for healthy Americans on how to eat a prudent diet, released Monday by the U.S. Department of Agriculture.

While the two previous editions (1980 and '85) have been criticized for being too general, the latest version gets more specific, particularly in the area of weight. Yet its recommendations for how much people should weigh are being questioned by some nutrition and weight loss experts for being overly generous. And its definition of reasonable weight loss as 1/2 to one pound a week may sound too conservative to the nation's 65 million dieters, who demand quick results, and to the many diet programs that thrive on that desire.

The guideline to "maintain a healthy weight" (changed from "maintain an ideal weight") focuses on the idea that losing weight for many people may simply be a matter of appearance, not health, and that the scale is not nearly as good an indicator of your healthy weight as is your body shape. While weight loss experts have been discussing these concepts for several years, USDA has combined them all into its definition of "healthy weight."

Thus, according to USDA, you are at a healthy weight if you meet all three of these conditions:

(1) Your weight is within the ranges of the height-weight table.

USDA has scrapped the long-used 1959 and 1983 Metropolitan Life Insurance tables in favor of the newer chart of choice based on body mass index, or BMI. The Metropolitan tables were based on a nonrepresentative population -- people who applied for life insurance and who had the longest lifespans. BMI is derived from height and weight and is correlated with body fat.

Based on a National Academy of Sciences report, USDA's chart is divided into two categories. But instead of the traditional demarcation between men and women, the chart is divided by age: 19- to 34-year-olds in one column, and 35 years and older in the other.

Thus, men and women are in the same weight ranges -- some that span more than 40 pounds for each height. (A footnote does mention that the lower weights in the ranges generally apply to women, who have less muscle and bone, and the higher weights would more often apply to men, who have more muscle and bone.) In the older age range, in particular, the chart lists higher maximum weights than either Metropolitan table.

Betty Peterkin, executive secretary to the Dietary Guidelines Advisory Committee and former acting administrator of the USDA's Human Nutrition Information Service, said that recent research has shown that men and women do not differ with respect to their healthy weight for height. Research has shown that individuals can be a little heavier as they get older without risk to health, according to Peterkin.

(2) You have a favorable waist-to-hip ratio. If your waist is bigger than your hips (apple shaped), you're at a greater risk for diseases such as diabetes, gall bladder, hypertension and heart disease than if you carry your weight around your hips (pear shaped).

To determine your waist-to-hip ratio, stand relaxed and measure around your waist near your navel. Don't pull in your stomach. Then, measure around your hips, over the largest part of your buttocks. Divide the waist measurement by the hip measurement. Results above .95 for men and above .8 for women are linked to a greater risk of disease.

(3) You already have a health problem, such as diabetes or hypertension, for which your doctor has recommended weight loss. Or, you need to gain weight for a medical reason.

C. Wayne Callaway, a committee member who took the leadership role in forming the healthy weight guideline, believes that the three criteria will identify those people who don't need to lose weight for health reasons, help deemphasize the nation's obsession with thinness and cosmetic appearance, and "stop this crazy on-again, off-again" dieting that leads to rapid weight loss and rapid weight gain.

Callaway acknowledged that there may be exceptions to the three conditions: naturally slender people (not those who are thin by virtue of an eating disorder or chronic dieting) may be at a healthy weight even if they are below the weight range. Conversely, people such as football players who are big boned and very muscular may be over the weight range and still be healthy.

William Castelli, director of the Framingham Heart Study, a project of the National Heart, Lung and Blood Institute, disagreed with the idea of separating the height-weight chart by age, contending that it's harder for individuals to tolerate extra pounds as they get older. "To go around and tell Americans to weigh more has got to be one of the feats of illogic in the United States," he said.

He also questioned the large weight ranges within each category. At 5 feet, 9 inches, Castelli should weigh between 142 and 183 pounds, according to the USDA chart. "That's skinny to obese," he said. "I'm fat when I'm at 170."

Mary Abbott-Hess, president of the American Dietetic Association, agreed that the weight ranges are wide, but said that the disparity emphasizes that people across a wide range are not at risk.

"Societally and emotionally, it's counterproductive to think that being a size 10 rather than a size 8 is unhealthy," she said.

As for the recommendation to lose only 1/2 pound to one pound a week, Abbott-Hess said that at first she thought it was "very conservative," and "not very comforting for those who need to lose a lot of weight." But then she realized that extremely obese individuals would probably be over USDA's maximum weight range, and thus would not fit into the definition of a "healthy weight" to begin with. Historically, dietitians and diet counselors have suggested that people lose between one and two pounds a week.

Callaway acknowledged that two pounds a week would probably be safe for a person who weighed 280 pounds, but "most healthy Americans don't have that much to lose." Previous recommendations to lose between one and two pounds a week were developed in the late '70s, Callaway said, when 300-calorie liquid protein diets were the rage. "One to two pounds seemed reasonable in comparison" to the weight loss the liquid protein diets were promising, he said.

USDA's rationale for the new, lower weight loss goal is based on the theoretical calculation that in order to lose two pounds a week, an individual has to eat 1,000 fewer calories a day. For a woman who normally eats 1,600 calories a day, that would mean a reduction to 600, too low to accommodate a nutritious diet. "Women have a hard enough time getting the calcium and iron that they need" at 1,600 calories, said Peterkin.

Martin Lobel, a Washington attorney who represented the Diet Center in congressional hearings last March about the safety of weight loss programs, said, "Nobody's going to follow this. You either want rapid weight loss or something you can follow. If I'm on a diet, which I'm on perpetually, if I don't see that scale clicking down one to two pounds a week, I get bored. Psychologically, people have to see results."

But Callaway said that the only way to sustain weight loss is to lose slowly and to concentrate on eating behavior, not the scale. In this respect, the guideline should help change the way people think, Callaway said. Successful weight loss, he said, "is a long term project."

Height.................Weight in pounds*.......Weight in pounds*

(without shoes)........19-34 years.............35 years and up

5'0"....................97-128**...............108-138

5'1"...................101-132.................111-143

5'2"...................104-137.................115-148

5'3"...................107-141.................119-152

5'4"...................111-146.................122-157

5'5"...................114-150.................126-162

5'6"...................118-155.................130-167

5'7"...................121-160.................134-172

5'8"...................125-164.................138-178

5'9"...................129-169.................142-183

5'10"..................132-174.................146-188

5'11"..................136-179.................151-194

6'0"...................140-184.................155-199

6'1"...................144-189.................159-205

6'2"...................148-195.................164-210

6'3"...................152-200.................168-216

6'4"...................156-205.................173-222

6'5"...................160-211.................177-228

6'6"...................164-216.................182-234

*Without clothes. ** The higher weights in the ranges generally apply to men, who tend to have more muscle and bone; the lower weights more often apply to women, who have less muscle and bone.

Derived from National Research Council, 1989.