Sue Richardson, 24, curled her thin, fragile frame on a couch in her parent's split-level home in Falls Church and reluctantly told her story. "It's really funny how it all got started," said Miss Richardson, who could easily be mistaken for a malnourished child.

"I went on a diet just to loose a few pounds. Before I knew it, I lost control and I couldn't stop losing weight," she told a visitor in a soft voice.

In less than a year, Miss Richardson's weight dropped sharply from about 100 pounds in the fall of 1974 to only 65 pounds by the end of the summer of 1975, when she finally was hospitalized.

Doctors at first thought Miss Richardson was playing a childish prank by refusing to eat. But her behavior later was diagnosed as "anorexia nervosa," a psychiatric disorder that drives its victims to self-starvation and sometimes death.

Miss Richardson is among a growing number of young women who are hospitalized each year with the illness sometimes called "starvation sickness." Those who suffer are almost always female Caucasians between age of 13 and 30. Only 4 per cent to 6 per cent of the victims are male; none has ever been black. Between 15 per cent and 21 per cent of all anorexics die of starvation and its complications.

Although anorexia nervosa once was though to be rare, doctors now estimate that the illness - which is on the rise in the United States, Britain, Sweden, and Italy occurs in one out of every 100,000 well-off girls. However, incidents of the disease can range as high as one in 300, according to figures obtained from the National Institute of Health.

Most anorexia nervosa patients are from middle or upper-income families. They generally are high achievers, physically hyperactive, extremely well-behaved, and would be considered "model children" by ordinary standards.

Dr. Hilde Bruch, a psychiatrist at the Baylor College of Medicine, Houston, Tex., and an authority on anorexia nervosa, maintains that anorexic girls are drawn into the illness by their desire to gain prestige and acceptance in a society that places great emphasis on body appearance.

"These girls take the TV commercials seriously," said Dr. Bruch. "They become caught up in overthinness. They believe they can achieve respect and special recognition by achieving thinness."

The first case of anorexia was described in 1685 by English Dr. Richard Morton. In July, 1684, an 18-years-old girl has developed amenorrhea apparently from "a multitude of cares and passions fo her mind," according to Dr. Morton's account. Subsequently her appetitie began to abate, and her digestion deteriorated. Over the next two years, she lost more weight and developed fainting spells.

Dr. Morton who was shocked by her appearance wrote: "I do not remembert that I did ever in all my practice see one, that was conversant with the living so much wasted with the greatest degree of a consumption (like a skeleton, only clad with skin.)

"Yet there was no fever, but on the whole contrary a coldness of the whole body; no cough, or difficulty of breathing . . . only her appetite was diminished and her digestion uneasy," wrote Dr. Morton. They young girl died three months after he began treatments.

"Today, 290 years after this young women's death we are still attempting to understand this puzzling illness," said Dr. Joseph A. Silverman, of the Department of Pediatrics, Columbia University College of Physicians and Surgeons.

Dr. Silverman, who has studied anorexia for the past decade, was among 40 experts on the illness from around the world who met last October at the National Institutes of Health for the first international conference on anorexia nervosa.

In a paper he presented, Dr.Silverman, who has treated 65 anorexia patients described the typical anorexia "a teen-age girl who is depressed, weepy, hostile, frequently agitated, and in seemingly constant motion." She usually wears heavy sweaters and slacks not only to mask her emaciation, but also to keep warm.

"In addition to feelings of perpetual chilliness, all complain of severe constipation, some having bowel movements fortnightly or even once monthly," Dr. Silverman said. "Skin changes are the commonest physical abnormality noted in teh anorexic. The skin appears dark and dirty; texture is rough and resembles fine sandpaper."

Dr. Silverman said that anorexics also develop long silken hairs found extensively over the trunk of their bodies, extremities, and sometimes on the face. There also is a loss of scalp hair, he said.

In anorexia nervosa, as in obesity, according to Dr. Bruch, the victim often is suffering from psychological disorders that distort her image of her own body and cause an intense fear of not being able to control eating habits.

Dr. Bruch, in her book, "Eating Disorders," said that both the anorexic and obese person usually have lost their ability to distinguish between hunger and other undesirable feelings during childhood development.

She said anorexic and obese patients suffer from "the basic misconception of not having an identity of their own, of not owning their body and its sensations, with specific inability of recognizing hunger as a sign of nutritional need."

"Anorexia," which means "loss of appetite," is a misnomer since many anorexics cannot exert continuous control over their eating habits and frequently go on eating binges.

They, in turn, lose weight through self - induced vomiting, diarrhea achieved by taking large doses of laxatives, or prolonged physical exercise - often to the point of complete fatigue and exhaustion.

Although anorexia nervosa patients behave abnormally toward food, they often busy themselves with activities that involved food and eating. Many are good cooks who receive vicarious pleasure in seeing others gorge themselves on rich foods. They also have an extensive knowledge of the caloric values of foods.

Female anorexics characteristically undergo amenorrhea (absence of menstruation) after losing substantial weight. They feel stuffed after consuming only a small amount of food and bloated if they gain even a few ounces. As their bodies slowly dwindle, the anorexic continues to deny that she is ill.

Sue Richardson said she was a senior at Lewis and Clark College in Portland, Ore., when she decided to go on a diet in the fall of 1974.

"I weighed a little over 100 pounds and I felt a little bloated," said Miss Richardson, who is a salesperson in a stationery shop. "My clothes were getting a little tight and I decided to diet and get back down to my ideal weight - about 95 pounds."

"I lost a few pounds and just kept on losing," she said. "Dieting became an obsession. It was really easy not to eat in the school cafeteria. You could throw nearly all of your food away and nobody noticed. I ate less and less. If anyone said I was looking too thin, I became really defensive."

When Miss Richardson returned to Falls Church for Christmas recess from college, her parents were startled at her weight loss. She was examined by the family doctor who said that her weight loss possibly was due to her heavier course load at school.

"I never saw myself as being too thin," she said. "I always looked to myself like I should lose just a few more pounds to get my weight where I wanted it to be."

After she graduated from college, Miss Richardson said she went to Africa as a Peace Corps volunteer. "Like everybody else who went over, I got dysentery," she said. "That made my weight problem just that much worse. When my weight got down to 65 pounds, my health was considered critical and I was sent back home."

After nearly a year tests and treatments by her family doctor, Miss Richardson said she went ot NIH where she was one of four anorexic being treated in the Section of Experimental Therapies.

Researches are split over which method is most effective in the treatment of anorexia nervosa. In one approach, individual psychotherapy is used to help the patient develop his own self awareness and independence after a brief period of hospitalization to help the patient gain weight.

Some doctors feel that anorexics should be hospitalized for an extended period to provide a controlled environment. The patient would first undergo psychotherapy as an inpatient then continue therapy for several years as an out patient.

Family therapy has been found to be effective in some instances and is promoted on the theory that anorexia nervosa is a family - caused illness and the entire family must be treated. Behavior modification, which is used on a series of "rewards" or "punishments" to bring about weight in, is considered by many to be the most effective treatment of anorexia.

Miss Richardson said she was hospitalized at the NIH for three months during which she was restricted to her room without such priviliges as mail, phone calls, or TV unless she ate a certain amount of food or gained weight.

As her weight increased, Miss Richardson said she was given more and more privileges. She was released from the hospital when her health was no longer endangered by her weight loss. Each week Miss Richardson, who currently weighs about 90, meets a group psychotherapy to discuss her illness with doctors.

Muriel Richardson, a pharmacist, and her husband, James, a forester for the U.S. Department of Interior, said they felt "baffled" and "helpless" as they watched their daughter losing weight.

"Sue has always been able to eat a tremendous amount without gaining weight," said Mrs. Richardson. "Sue was the kind of kid that if you had a group of children together and you wanted someone to spur them on to eating, you'd put Sue at the table. She'd eat anything."

Another anorexia patient, who asked to remain unnamed in this article, is 23 and recent graduate of George Washington University. She grew up in New York City, where both her parents were psychiatrists and experts in psychoanalysis.

"My parents decided to move from New York to Toronto in 1970 and I refused to go along," she said. "When I finished the 11th grade in high school, I arranged to skip the 12th grade and go directly to Elmira College.

"At college, I got involved with a guy. We lived together. I got heavily involved into alcohol and smoked a little marijuana. All of a sudden I started gaining a lot of weight," said the patient, who noted that her weight shot form 115 pounds up to 145 pounds.

"I was drinking almost every night and I felt as fat as a blimp," she said. "When I went home from college, my mother kept telling me that I looked awful and I should lose some of the weight so I could look nicer."

"I began dieting. I didn't have a goal weight or any concept of what I wanted to eventually look like. I just wanted to look more like my mother, who was 6 feet tall and weighed 130 pounds.

"The skinner I got the more I looked like my mother. The more I looked like her, the better it made me feel because my mother was my ideal ," she said.

The patient said her mother eventually became ill with cancer and her father had a heart attack. A younger sister was arrested for prostitution. A younger brother became the leader of a homosexual organization.

"I was cooking and preparing meals for everybody in the house," she said. "I prepared the special bland diet for my mother, a special diet for my father and regular food for the rest of the family.

"It seems that the onset of my anorexia, which I was not aware of at the time, ran parallel with my mother's illness with cancer," she said. "The sicker she got, the worse off I became."

The patient said her mother died in September, 1975, when the patient's weight had reached a low of 75 pounds.

"My mother had me on 600 calorie diet. She said that was the only way a person could lose weight," the patient said. "I use to carry around a small vial containing exactly three level teaspoons of coffee creamer containing 33 calories each. I knew that was all the calories allowed each day for coffee.

"I knew the caloric value of every ounce of food and I ate and I lived way beneath the 600 calories diet my mother had put me on," she said.

During a family vacation in Aruba on the north coast of South America shortly after her mother died, the patient said she discovered by accident that she that she could eat anything she wanted and not gain weight is she vomited the food up after the meal.

"I remember thinking to myself that I had discovered every American woman's dream: to be able to eat whatever you want and still not gain weight," she said. "I became very scientific about throwing up. I got so I didn't even have to put my fingers down my throat to make it happen."

The patient said that she first became aware that she was suffering from a serious illness in October, 1975, when a man on a Washington street saw that she was so weak she could hardly stand and insisted that she go to a hospital. She is now in the care of a psychotherapist.

Currently, the patient weighs 115 pounds and is following a frequent pattern of binge eating and throwing up. "I look into the mirror and I see myself as grotesquely fat - a real blimp," said the patient, who wore a thick , wool sweater during the interview. "The pants I used to wear are very tight now. When I walk down the street, I waddle, because I think I'm so fat."

In 1973, another anorexic, who must remain anonymous, gave doctors at NIH a graphic description of her struggles with anorexia nervosa.

"I never weighed more than 102 pounds and I started getting down to like 98 pounds. I thought it was really kind of interesting - kind of freaky," she said.

"I was always happy when I would see other people eating, but as far as I was concerned, I didn't want to touch it," she added. "I would put something on somebody else's plate and in order to satisfy myself and to make myself feel that I was having a small portion and people would not think I was a pig, I would put like fout times the amount of food on the other person's plate.

"I'd put a normal amount on my plate," she said. "I'd say, Ah, look at me! I'm eating like a big pig.'"

"If I go on a binge, I eat a lot, I throw up," she said. "Either I throw up naturally because my stomach is so full or I make myself throw up. Or I've taken laxatives, like every other day. I'd take overdoses of them."

"I want to be really super, superthin," she said. "I don't know why I feel this way and I wish I didn't."

At last report, this patient had gained some weight, but still was preoccupied with thougths of food, according to one of her doctors.