A small order of McDonald's Chicken McNuggets contains twice as much beef fat as a regular McDonald's hamburger. A triple cheeseburger from Wendy's accounts for a whopping 1,430 calories. An otherwise low-calorie spud is turned into a 650-calorie meal when it is transformed into Arby's Deluxe Potato.

Those are among the findings published in "Fast Food Eating Guide" by the Washington based health advocacy organization Center for Science in the Public Interest. In an attempt to educate patrons of fast-food eateries, the organization has compiled the calorie, fat, sodium and sugar content of foods served by 13 such purveyors. The chart, with colorful graphics and consumer tips, is available for $3.95 ($7.95 for a laminated version) by writing CSPI, 1501 16th St. NW, Washington, D.C. 20036.

Based on the National Academy of Science's recommended daily intake of no more than 1,100 to 3,300 mg of sodium, and the CSPI's suggested fat intake of no more than 10 to 15 teaspoons per day, the chart also offers a "gloom" rating for each food. This factor represents the overall nutritional value of a food or meal in a single number: the lower the gloom rating, the better the food. The average person, notes the chart, should not consume more than 50 to 100 gloom points a day. A Wendy's meal of the aforementioned triple cheeseburger, a cola and french fries -- with 19 teaspoons of fat, 1,958 mg of sodium and 7 teaspoons of sugar -- arrives at a gloom rating of 105, the guide's highest among lunch and dinner meals.

The guide is but one of CSPI's food-related projects. Among other initiatives, the organizationn is pushing for more whole-grain breads; more raw, fresh fruits and vegetables; and complete ingredient and nutrition information for all foods on the menus of the nation's fast feeders. A few changes are already under way: Denny's recently began promoting the fact that it uses vegetable oil, as opposed to the more saturated beef fat, in its cooking. And just last month, Burger King switched from beef tallow to vegetable oil in the preparation of its chicken, fish and onion rings. (It still uses beef fat for cooking french fries.) Bonnie Liebman, CSPI's director of nutrition, is encouraged by the changes. "Restaurants that are willing to compete on the basis of nutritional value," as opposed to gimmicks, are a trend the center would like to see increasing, she noted.

Fast food needn't be synonymous with bad food, and the "Fast Food Eating Guide" demonstrates how to confront a menu healthfully by skipping sauces (ask for extra lettuce and tomato), discarding breading, and opting for smaller portions. The guide suggests choosing baked or broiled fish when possible. At breakfast, order items such as orange juice, pancakes, muffins and plain toast; avoid offerings such as egg sandwiches, croissants, sausages and biscuits, which tend to be both high in sodium and greasy. At the salad bar, skip the bacon bits, croutons and fried noodles.

An at-home adaptation of two fast-food favorites -- french fries and a chicken sandwich -- is featured in today's Express Lane menu. The "french fries" are actually oven-baked, and the chicken is skinned and broiled, served between slices of whole-wheat bread. Salt (if desired), pepper and vegetable oil are all you'll need on hand prior to a trip to the market.

Express Lane list: Potatoes, chili powder, chicken breasts, lemon juice, dijon or meaux mustard, tarragon, whole-wheat bread, watercress or alfalfa sprouts. OVEN-BAKED FRIES (4 servings) 1 1/2 pounds large baking potatoes, scrubbed 1 teaspoon chili powder 2 teaspoons oil, preferably safflower 1/4 teaspoon salt (optional)

Place a baking sheet in a 400-degree oven while preparing the potatoes. Cut the potatoes lengthwise into 1/2-inch-thick slices. Cut each slice lengthwise into 1/2-inch-thick strips and put them in a large bowl. Toss the strips with the chili powder to coat them evenly; sprinkle on the oil and toss again.

Arrange the potato strips in a single layer on the hot baking sheet. Bake the strips for 20 minutes, then turn them and continue baking until they are crisp and browned -- about 20 minutes longer. Sprinkle the fries with salt if desired, and serve hot. From "Fresh Ways with Vegetables," by the Editors of Time-Life Books (Time-Life, $14.95, 1986) BROILED-CHICKEN SANDWICH ON WHOLE-WHEAT BREAD (4 servings) 4 boneless chicken breasts, skinned Freshly ground pepper Vegetable oil 1 to 1 1/2 tablespoons lemon juice 3 tablespoons dijon or meaux mustard 1 tablespoon tarragon 8 slices whole-wheat bread, toasted or grilled Watercress or alfalfa sprouts

Trim the chicken of fat and shape into a rectangular piece of meat; pound it to flatten. Dust with a liberal grinding of pepper and brush lightly with oil. Place chicken on a lightly oiled baking pan and cook under a preheated broiler, about 2 1/2 minutes per side. Combine the lemon juice, mustard, and tarragon in a small bowl and spread mixture on one side of each breast. Place one breast between 2 slices of bread, spreading with additional mustard if desired and topping the chicken with watercress or sprouts.