THERE ARE no fat ladies in this circus. In the modern-day Ringling Bros. and Barnum & Bailey Circus, the performers keep fit. Their bodies, after all, are their business. And it's a tough business.

The animals, however, don't have to work at it. When they're not performing, they lounge in the catacombs of the D.C. Armory, the elephants downing up to four barrels of hay daily, the horses and camels breakfasting on oats mixed with sorghum, the giraffe feeding on his nightly grain salad.

But the other performers--the animal trainers, the acrobats, the high-wire artists -- can't be as casual. Living and cooking on the train, locating supermarkets in new cities and timing meals between performances are no simple feats -- especially with eating healthfully as a constant concern. "Everything's done in moderation," says showgirl Judy Nightingale. "Otherwise you pay for it immediately."

All the performers have cooking facilities on board the circus train (20 showgirls in car 44 with six refrigerators, 17 clowns sharing a car and a microwave). Others, the families in particular, live and cook in less-crowded quarters, some following the train in their own trailers.

Car number 45 is reserved for those members of the cast and crew who don't have the time or inclination to cook. It's the dining car, or pie car, where anyone can grab eggs and fried potatoes before the early show, or a "mainline" dinner -- likely to be some variation of meat and potatoes -- after the night show. In the pie car, it's standard American fare ("they don't cater to Bulgarian delicacies here," jokes clown Shaun Hebert), offered with a list of "Pie Car Conduct" almost as long as the menu. (Among the rules: "If you do not have time to eat, this is your responsibility, not ours.") This is no ordinary Amtrak cafe; the facilities live up to a short-order grill rather than just a snack bar. It's decorated with red-checked curtains and circus posters. Booths enough for 30 people double as storage space for pudding boxes and potatoes, and there is a walk-in refrigerator and a freezer.

At the D.C. Armory, the circus members and animals feed side-by-side between shows, the "junior pie car" being next-door to the animal feeding area. For the people, bathrobes and jeans is the dress code here; performers are prohibited from wearing their on-stage garb while eating. Costumes are costly and must be kept in good shape for two years.

As for the concession food--prepackaged purple cotton candy, commercially bagged peanuts--the audience may find it palatable, but many of the performers prefer to keep away from it.

Once a week a bus takes the circus to the market so the staff can do shopping and laundry. For the animal feeders, though, shopping is a gargantuan task: Over the past year, the circus animals have downed 1,144 tons of hay, 135,000 pounds of oats, 728 dozen eggs.

The human performers have even more varied feeding habits. Here then, is their list: The King of the Jungle

Gunther Gebel-Williams is, like the program description of his tigers, a "cannily cunning carnivore." It takes five meals a day -- one of which is always meat -- to fill the cavernous rib cage of Gebel-Williams. Visible under his Liberace-style vest, the trainer's sleek stomach certainly doesn't show the effects of the German food his wife Sigrid makes.

She knows to avoid oil or butter for his pre-show meals because it upsets his stomach. He hates anything microwaved, and a TV dinner "would be call for divorce." No dips or potato chips in the house. No new foods. And like his tigers, he "would have a growling stomach" if she cooked him a cheese casserole instead of a steak.

When the show is in Washington, Sigrid drives to Baltimore to buy her husband a special German ham and rye bread that she can't find here. Her affection for her husband even extends to his animals -- when two leopards and a lion were recently weaned, Sigrid found herself fixing formula for them daily.

The Trapezist

This circus may not still be "The Greatest Show on Earth," but Anna Farfan is the sveltest 37-year-old on two legs. "You get overweight and you don't fly," says the Czechoslovakian mother of two flying sons, aged 18 and 14. For her, overweight means anything over 118 pounds. She takes 14 vitamins a day, and dinner -- at 1:30 a.m. -- concentrates on fruits and vegetables. The trapeze diet, of course, has built-in motivation; an extra pound may mean the difference between flight and flop.

The Little Man

Serf Rocha, the little person of the circus who likes to say he's "short on time" and that he has "a short life" -- is big on eating. Before running over the backs of four elephants, Rocha eats a bowl of cereal, vitamins and orange juice. He likes Mexican food and cook-outs, and his wife makes "a great spaghetti."

The Tall Man

"Guinness Book of World Records" winner John Russell says he has a "high metabolism." No wonder -- he stands 20 feet, 1 3/4 inches tall (even though 14 feet of it was aluminum tubing). It gets pretty shaky up there, says Russell. His stilts wobble and he has difficulty getting around the track if he doesn't eat before a show. Omelets are high on his list.

The Motorcyclist

As to be expected from daredevils who zoom inside steel-meshed globes at 60 miles per hour, Jose Medina fuels himself with jalapeno peppers for breakfast.

The Bear Trainer

Wally Naghtin cooks the "traditionals," like fried chicken, in his trailer. His bears (who behave better on stage than backstage) get more variety: Hills Revena's Omnivore bear food, carrots after the afternoon show, sometimes honey.

The High-Wire Walkers

They must have a well-balanced diet, of course. But the Carrillo Brothers say they can eat as much as they want because they get plenty of exercise.

The Showgirls

When Judy Nightingale dangles from a rope looped around her neck, she can really feel it if she's too heavy. For spinning and hanging upside down, a protein bar will hold her.

The showgirls are big on protein, mostly high-voltage drinks of bone meal, lecithin, yeast and protein powder. And many of them are vegetarians, so salads are a mainstay. No wonder they're so diet-conscious; every Friday is weigh-day. Being overweight is frowned upon since that may mean refitting their costly costumes. But their daily workouts make them all look as if their weightiest parts are their false eyelashes.

The Clowns

They eat like elephants. Because they run around so much, they never worry about gaining weight. There are vegetarians among the clowns, says clown Sean Emery, but tastes vary among co-clowns in his car; someone may be cooking grainburgers next to someone cooking a roast. For him, a smoothie--a pure'e of peaches and apple juice--does the trick before the show.

The Acrobats

To digest for somersaults, Rado Pulen fills up on Bulgarian cooking at least two hours before showtime. If he puts on weight, his partners, too, must carry it.

Here are some of the performers' recipes.

HIGHWIRE SACOCHO (Pedro Carrillo's Colombian Soup) (10 servings) 1 pound yucca (available at Latin American markets), peeled and sliced 1 pound potatoes, peeled and cubed 3 green plantains, sliced 1 medium green cabbage, sliced 3 pounds soup meat, cubed, with bones 5 cloves garlic, minced Cumin, salt and pepper to taste Parsley

Place cut vegetables, meat and garlic into pot and add water just to cover. Bring to a boil, then reduce heat to a simmer. Cook until meat is done and vegetables are soft, about 1 1/4 hours. Season to taste while cooking. Add parsley and serve.

FLYING FRYING (Anna Farfan's Wiener Schnitzel with Potato Salad) (6 servings)

Wiener schnitzel: 3 1/2 pounds veal steaks 3 eggs Pinch of salt Bread crumbs Oil for frying

Potato salad: 6 medium-sized potatoes 4 hard-cooked eggs 8 ounces canned green beans, drained (or substitute fresh) 8 ounces canned carrots, drained (or substitute fresh) 8 ounces canned wax beans, drained 5 small dill pickles, chopped 1 tomato 1/8 teaspoon salt 1 cup mayonnaise

To prepare wiener schnitzels, cut meat into thin slices and pound thinner. Beat eggs with the salt. Cover both sides of the schnitzels with the beaten egg, then roll in bread crumbs. Place schnitzels in oil in frying pan on medium heat. When oil is hot, cook schnitzels for four minutes on each side.

To prepare potato salad, first boil potatoes, peel and cool them. Chop hard-cooked eggs. Slice potatoes and add eggs in a large bowl. Add canned or fresh vegetables. Add pickles, salt and mayonnaise. Mix and serve with schnitzels.

SHOWGIRL CLAM BISQUE (Judy Nightingale's Soup) (6 to 8 servings) 2 4 1/2 ounce cans clams 1/2 cup chopped celery 1/4 cup chopped onion 4 tablespoons butter 3 tablespoons flour 1 teaspoon salt Dash of white pepper 2 cups milk 2 cups light cream 2 teaspoons lemon juice or 1 teaspoon curry powder

Drain clams, rinse and chop. Saute' celery and onion in butter until tender, but not brown. Blend in flour, salt and pepper. Add milk and light cream, stirring constantly. Cook and stir until sauce is smooth and has thickened. Add chopped clams and lemon juice or curry powder and heat.

PIE CAR BIGOS (Sauerkraut and cabbage) (8 to 10 servings)

A recipe of two Polish teeterboarders, this is frequently made in the pie car. 1 medium green cabbage 2-pound jar or bag of sauerkraut 2 teaspoons salt 2 to 3 tablespoons oil 1 pound stew meat, cubed 1 pound pork, cubed 1 pound kielbasa, sliced 6 to 7 slices bacon 5 dried Polish mushrooms, chopped (optional) 1 chili pepper, diced Salt and pepper 6 ounces tomato paste 3 bay leaves

Shred cabbage and combine with sauerkraut (drain most of juice) in a pot. Fill with a quart or so of water and 2 teaspoons salt, boiling until cabbage is soft. Pour off excess water to stew-like consistency. In hot oil, fry cubed meat, sliced sausage and bacon. Add to cabbage along with chopped mushrooms and chili pepper. Mix salt and pepper with the tomato paste and stir into cabbage along with the bay leaves. Continue to simmer for about 20 to 25 minutes. Recipes from "Center Ring Circus Cuisine"