Eat a variety of foods in moderation. Follow a balanced diet. To coax Americans into eating properly, nutritionists and health officials have been giving advice like this for years. But what do these statements really mean? What is a variety of foods? Isn't one person's definition of moderation another's gluttony?

"Balance. Moderation. Variety. It almost sounds like we're beating around the bush or being intentionally vague," said Susan Krebs-Smith, acting chief of the U.S. Department of Agriculture's diet appraisal research branch. "I agree they're vague."

In fact, Krebs-Smith found that while nutritionists generally believe that the key to an optimal diet is eating a variety of foods, even the nutrition community is divided in its interpretation of that phrase.

The problem is that recommendations for the public are necessarily general. "Because we have people in all sizes and shapes and different needs, you can only use guidelines as guidelines," said Jayne Newmark of the American Dietetic Association. "They will be different for a six-foot-tall man who weighs 180 pounds or for a woman who is five feet tall and weighs 100. A pickle might be a bad food for someone who has high blood pressure but not necessarily for someone who doesn't."

Thus, the interpretation of "moderation" and "variety" is most often left to the individual.

Moderation "means something different to everybody, which is why the food industry loves it . . . and why I don't," wrote Jayne Hurley, associate nutritionist for the Center for Science in the Public Interest in the consumer group's Nutrition Action Healthletter. Hurley contends that these rather nebulous terms are a smokescreen that manufacturers use to avoid tougher advice to cut down on fat, salt or other substances.

In an analysis of USDA's food consumption surveys, Krebs-Smith found that people who ate a wider variety of foods had higher intakes of vitamins and minerals. (The average number of different foods eaten in three days was 22.) Nevertheless, variety had no effect on the amount of fat, sodium, sugar or cholesterol people ate. In other words, just because people ate a variety of foods didn't mean their diets were low in fat or cholesterol.

And that's what bothers Hurley. "Most Americans suffer not from eating too little, but from eating too much saturated fat, cholesterol, salt and sugar," she said.

Marion Nestle, chairman of the department of nutrition, food and hotel management at New York University and managing editor of the 1988 Surgeon General's Report on Nutrition and Health, said she believes "the real issue is political."

When it comes to federal dietary guidance, "it has to meet the needs of the constituency," she said. Terms such as " 'moderation,' 'variety' and 'all foods are good foods' are all ways of expressing a kind of guidance that doesn't hurt any of the food industries," she said.

Nestle said that while there was pressure from the meat industry that the Surgeon General's report not include advice to eat less meat, the report's final recommendation to "eat lean meats" was not a result of successful lobbying on the part of the meat industry. There were "a lot of people involved in the report who believe that all foods have a place in the diet and you can't tell people not to eat certain foods," she added.

The tendency for government health officials to avoid recommendations to eschew certain foods is illustrated in the ongoing revision of the U.S. Dietary Guidelines, a list issued by USDA. According to the draft, for example, the guideline to "avoid too much fat, saturated fat and cholesterol" is being rewritten to read "choose a diet low in fat, saturated fat and cholesterol."

The change "sends a more positive message," said James Heimbach, administrator of the USDA's Human Nutrition Information Service. "It puts the stress on a total diet rather than specific nutrients or individual foods," he added.

While some nutritionists believe dietary advice must be more specific, Heimbach disagrees: "If nutrition science were ready to support quantitative statements, we'd be making them." Heimbach said he supports the idea that there are no "good" or "bad" foods. Many nutritionists believe any food -- even "junk" foods like potato chips and candy bars -- can be part of a healthy diet if eaten in small quantities and not substituted for more nutritious items.

"Any food in its proper place in the diet can be a good food," Heimbach said. "Any food that is overconsumed can become bad. A Twinkie diet would not be overwhelmingly healthful but neither would a pineapple diet," he said.Eating Right appears on alternate Tuesdays.