If your idea of a light lunch is a bowlful of pasta salad, you are in for a shock. Staffers at the Center for Science in the Public Interest, wondering why pasta salad seemed to many to be so slimming when it looked to them to be pretty greasy, have conducted a small survey.

The conclusion: "Consumer beware," says Michael Jacobson, director of CSPI. "Pasta salads are out there to expand your waistline."

The survey, involving 10 pastas from delis in Washington and New York, 10 packaged pasta salads and four fast-food pasta salads, showed that fat contributed 40 to 60 percent of the calories in most of the pasta salads. A 3/4-cup serving of an average pasta salad with 3 3/4 teaspoons (4.4 teaspoons equals 1 gram) of fat would take up 25 percent of the daily fat allotment for an average person consuming 2,000 calories a day.

"And a lot of people eat considerably more than 3/4 cup; that's a lot of fat," says Jacobson. A main meal of 1 1/2 cups of pasta salad could contain the same amount of fat as a fast-food order of a hamburger, french fries and a milkshake.

"A good portion of the fats come from cream or meat, so it is saturated fat as well," says Jacobson, adding that the biggest improvement anyone can make in his diet is to cut down on saturated fats.

The fattiest salad turned out to be Pasta Carbonara Salad, served by Balducci's of New York City. The dish, a creamy mixture of corkscrew pasta, prosciutto ham and onions with a cream and Romano cheese sauce, contained a gut-expanding nine teaspoons of fat and 486 calories per serving.

"Balducci's was a bit of a shock; nine teaspoons is an enormous amount of fat in a modest serving," said Jacobson. "It was clearly the worst."

The American Cafe in Washington, on the other hand, received laurels for its low-fat Sesame Noodles, which contained only 1.5 teaspoons, or 25 percent fat, for every serving.

Of the packaged salads, Mueller's Creamy Italian pasta salad was the greasiest, with 7 1/2 teaspoons of fat and 435 calories in every serving, two-thirds of the calories coming from fat.

CSPI decided to conduct the survey when it saw the rise in popularity in pasta salad for what it saw as the wrong reason, according to Jacobson. "We see pasta salads as one of the new kinds of foods. And we are finding that people who eat it think it's very healthful, which is not true. Also, we did this survey as an incentive to the delis to cut back on the grease."

To wade through the choices of pasta salads, Bonnie Liebman of CSPI suggests that pasta salads dressed with oil rather than mayonnaise are less fatty -- the reason being that it takes less oil to coat and moisten the same amount of noodles.

If you like your pasta but don't like the fat, try the version below.

Express Lane List: chicken broth, smooth peanut butter, soy sauce, ginger root, garlic, sesame oil, red pepper, spaghetti, scallions, peanuts CHINESE COLD NOODLES IN SESAME SAUCE (2 servings)

3 tablespoons chicken broth or water

2 tablespoons smooth peanut butter

1 tablespoon soy sauce

1/4 teaspoon minced pared ginger root

1/8 teaspoon minced fresh garlic

1/2 teaspoon Chinese sesame oil

Dash ground red pepper, or to taste

1 cup cooked thin spaghetti, chilled

1/4 cup chopped scallions

1/2 ounce shelled roasted peanuts, chopped

In small saucepan combine broth, peanut butter, soy sauce, ginger and garlic and cook over medium heat, stirring frequently, until mixture comes to a boil; remove from heat and stir in oil and pepper. Transfer to small bowl, cover with plastic wrap and refrigerate for at least 30 minutes.

In serving bowl combine spaghetti with sauce and toss to combine; sprinkle with scallions and peanuts.

222 calories per serving.

2.5 teaspoons of fat. From "Weight Watchers New International Cookbook" (NAL Books, 1985)