Registered dietitian Debra Mattes-Kulig launched a computer diet analysis firm from her Arlington home last January. Now, as president of Bite by Bite, Mattes-Kulig uses her own personal computer to evaluate the diets of pregnant women, sports enthusiasts, people who want to lose weight, children who are picky eaters, and others concerned about what they eat and how it will affect their health.

"I'm in the business of health promotion," says Mattes-Kulig, who charges $10 for the computer diet analysis and $25 an hour for the subsequent dietary counseling. (She also counsels groups, and provides individual dietary analyses to all those in the group.) During the dietary consultation, Mattes-Kulig interprets the computer printout, develops a weekly food plan, and suggests menus and recipes that will fit the client's food preferences and life style.

"It's important to have a registered dietitian do the interpretation," says Mattes-Kulig. "They are aware of the limitations of their computer programs." In fact, she says, interpretation of the dietary analysis without a nutrition professional can be misleading, since a lay person might assume he is deficient in a nutrient when he is really not -- and begin taking a supplement he doesn't need.

Mattes-Kulig rarely recommends supplements. Since dietitians look at the diet as a whole, she says, often the addition of a few foods to the diet will take care of several nutrients for which intake might be low.

Mattes-Kulig purchased the basic computer program on nutriton that translates foods into nutrients from a programmer who was not a nutritionist. Then she put in many painstaking hours revising the software, which now contains nutrient values for more than 850 foods and analyzes intake for 29 nutrients, including sodium, saturated and unsaturated fat, fiber and cholesterol.

Clients record their food intake -- an experience akin to a confession for some -- for three days, usually two weekdays and one day on the weekend. They also fill in personal data, such as age, sex, weight, height and activity level. (Most people tend to underestimate their portion size, says Mattes-Kulig, and overestimate their activity level.) The personal data tells the computer which set of Recommended Dietary Allowances (based on age and sex) to use as the standard for comparison.

When nutrient intake is below the RDA, the computer prints out a list of 15 foods that are a source of that nutrient.

For potassium, for example, among the foods listed are bananas, cantaloupe, raisins and broccoli. When intake is too high in certain areas, such as for sodium and cholesterol, the computer identifies the foods in the person's diet that are the culprits. Because the RDAs are guidelines set intentionally high to cover the needs of the entire population, two-thirds of the RDA is considered an adequate intake by most nutritionists.

People love the "high-tech" aspect of the dietary analysis, notes Mattes-Kulig, who now prints out the analyses on computer paper rather than plain white stationery because her clients prefer it.

Some of the people Mattes-Kulig has advised:

*A woman in her seventh month of pregnancy with a poorly balanced diet. Not a milk drinker, the woman was not getting enough calcium and fiber, and she needed to increase her intake of complex carbohydrates. Mattes-Kulig reviewed foods high in calcium with the woman, who planned to breastfeed her baby, assuring her that it was still not too late to begin eating a more nutritious diet.

Mattes-Kulig prefers to see women earlier on in their pregnancy, or even before they become pregnant. "They are one of the groups of people who never have an opportunity to see a dietitian," she notes. "They're never sick and never in the hospital, and that's probably the only place they're going to come in contact with a dietitian."

*The parents of a 3-year-old with a very limited diet who was not getting enough calories. The child's parents were also picky eaters, so the boy never had an opportunity to enjoy a wider variety of foods. "Children learn from their parents. You are their biggest role model," says Mattes-Kulig. She encouraged the parents to offer the child a greater variety of breads, juices and vegetables, instead of always serving white bread, apple juice and the same two or three vegetables. Mattes-Kulig also provided other tips, like serving raw vegetables with a peanut butter dip and adding nonfat dry milk to meatloaf.

Computer diet analysis can be especially helpful for children who are picky eaters, notes Mattes-Kulig, since it is easier, less costly and in most cases more accurate than a blood test in determining if a child is really undernourished. Often, she says, parents are overly concerned, and diet analysis can help allay their fears.

*A 400-pound man whose dietary record showed he consumed more than 5,000 calories a day. (One meal included, among other foods, six tacos, a pint of ice cream, and two Diet Cokes.) Mattes-Kulig spent an entire session with him discussing the dangers of a high-fat diet and the foods in his diet with a high-fat content. The man had a sedentary job that required him to dine out often, so Mattes-Kulig went over restaurant menus with him, to show him how to choose foods low in calories, fat and sodium.

Because the man needed more than several dietary counseling sessions, Mattes-Kulig urged him to take a class about weight loss that she teaches at Alexandria Hospital to help him deal with the many possible causes of his overeating other than poor nutrition, such as lack of exercise, stress and emotional reasons. He has taken the class and has begun swimming regularly. "He's done really well," says Mattes-Kulig.

Most people don't bother to plan their week's worth of menus in advance, something Mattes-Kulig encourages in her dietary counseling sessions. "You just can't go into a grocery store and pick things off the shelf and have a balanced diet," she says.

Here are some recipes Mattes-Kulig provides her clients: CRISP AND FRUITY YOGURT SALAD (4-6 servings) 1/2 small head cabbage, shredded (2 cups) 15-ounce can pineapple chunks, well-drained 11-ounce can mandarin orange sections, drained 1/3 cup light raisins (optional) 1 cup seedless grapes (optional) 3/4 cup edam cheese (optional) 2 8-ounce cartons lemon yogurt

Place cabbage, pineapple chunks, orange sections and any optional ingredients in a serving bowl. Spread yogurt over salad and refrigerate until serving time. (This salad can be put in a thermos or individual plastic container with a lid and brought for lunch.) PASTA PRIMAVERA (2 servings) 4 ounces linguine 2 tablespoons butter 1 cup fresh broccoli, thinly sliced 1 medium carrot, thinly sliced 1/2 cup scallions, sliced 1 clove garlic, minced 1 teaspoon dried basil, crushed 1/2 teaspoon salt 1/4 teaspoon pepper 1 1/2 cups fresh mushrooms 1/4 cup dry white wine Grated parmesan cheese

Cook linguine in boiling salted water until tender; drain and keep warm. Meanwhile, melt butter in 10-inch skillet. Stir in broccoli, carrot, scallions, garlic, basil, salt and pepper. Cook 6-7 minutes or until vegetables are just tender. Add mushrooms; cook about 2 minutes more or until mushrooms are tender. Add wine. Cover and cook 2 minutes. Stir in cooked linguine; toss. Turn mixture into serving bowl. Sprinkle with parmesan cheese.