She was always cold. It didn't seem important at the time.

She had gone from a size 6 to a size 2. It wasn't a problem. Sweats come in all sizes.

She was a runner, a world class athlete. She was also well on her way to becoming an anorexic.

"You say anorexia and you think of someone so thin, someone in the hospital with veins sticking out," Marianne Dickerson says. "I didn't look like death. I was 5 foot 4 1/2 and weighed 96 pounds. I thought I looked normal."

She was a convert, a true believer in the new puritanism: Less is more. The more she ran, the more weight she lost. Pounds dropped along with her times. Life was orderly. Success was measured in miles and pounds and records.

One day in August 1983 she found herself on the starting line of the first world championship marathon for women, surrounded by the lean exemplars of her sport. It was only her third marathon, her second in eight weeks. No one knew who she was. Twenty-six miles later, she was in third place.

Entering the stadium in Helsinki, she thought about her father, who had said, "I don't care how you do, just beat the damn Russians." She could see Raisa Smekhnova, the Russian, 10 yards ahead of her. She thought, "What's my Dad going to say?"

Approval and ambition and discipline propelled her forward. She passed Smekhnova on the last curve. They draped the silver medal around her neck and she said, "Oh, there's lots left, I just know there is."

She was wrong. Dickerson has not run a marathon since. Her body refused to collude with her obsession. It was feeding off itself because she was not feeding it enough, burning muscle because there was no fat.

"I look at the picture of me crossing the finish line and I think, 'Geez, I can't believe I looked like that,' " she says. "How the hell did I run? I looked like a little stick."

In her freshman year of college, she ate chocolate sundaes and weighed 116 pounds. Then diet sodas and lo-cal bread became her staples. No carbohydrate loading for her -- the night before the race she binged on fried spinach patties and strawberry ice cream. Now she remembers that sometimes she felt hungry.

"I never want to feel that way again," she says. "I remember feeling weak. I remember feeling tired. I could run, but in terms of brute strength, I didn't have any. I kept thinking, 'If a strong wind came, it would blow me away.' "

She is eating again and training again and running again. Today she will compete in the Nike Cherry Blossom 10-mile race around the Tidal Basin. But sometimes she thinks about the irony of athletes who must survive their own fitness.

It is the era of good times and good bodies, of calipers and skin folds and body fat percentage. Lean has replaced lithe as the ultimate in body language. Marianne Dickerson knows how easily this can become a form of tyranny.

"The thinking is, one of 150 young women between 12 and 16 will become anorexic," says Jean Rubel, president of Anorexia Nervosa and Related Eating Disorders Inc. "I heard another figure at a conference recently, that one-third of all adult women are dealing with eating disorders -- anorexia, bulimia and obesity. I think that's low.

"An awful lot of athletes are involved in anorexia and bulimia. Why? We're living in a screwed-up culture where the trim, fit athletic body is a guarantor of success, happiness and self-esteem."

Experts say there are no reliable statistics on the extent of the problem among athletes. Estimates vary.

"It's getting to be an epidemic," says Doug Brown, administrator of Athletics West, a track club for world-class athletes, including Dickerson, in Eugene, Ore.

"It's common in athletes and it's common in runners," says Dr. Robert Voy, chief medical officer for the U.S. Olympic Committee. "It is not of epidemic proportions as far as I know."

"The real problem is we don't know how much of a problem it is," says Jack Wilmore, professor of physical education and surgery at the University of Arizona. "I've heard reports that 25 to 30 percent of the women athletes in gymnastics and diving may be affected. With the divers, the emphasis is on looking good for the judge in their bathing suits."

Pan Fanaritis, women's track coach at Georgetown, says, "Half the kids on my team have the latent anorexic tendencies. I'd say 30 to 50 percent of female distance runners have the potential to encounter related type problems."

Scott Pengelly, a sports psychologist at Athletics West who has worked with Dickerson, says he has seen one new patient a month since last May -- this after not seeing any anorexics in the previous five years.

"It's so sad, it's rampant," Dickerson says. "I can't tell you the number of runners who start out a little heavy and you see them the next year and you wonder if it's the same person."

Marianne Dickerson was discovered. "For six weeks after the race, I was on cloud nine," she says.

There were interviews and offers. She didn't take time off. She was motivated. "I trained and trained and trained and then all hell broke loose. I got a pain in my lower right back, the pelvic area. Stupid as I was, I thought, 'It will go away.'

It didn't. She ran until she couldn't walk. "For the next six or seven months, it was a nightmare," she says. "I was like a car that just quit. My body didn't run."

She was diagnosed as having an inflammation of the sacroiliac joints. She took anti-inflammatory drugs and developed anemia. She had already stopped menstruating. Her skin turned dry. She went to doctor after doctor. A few even suggested she gain some weight.

Rubel says, "The clinical definition of anorexia is a 20 to 25 percent loss of ideal body weight. I would consider her an anorexoid."

"I said, 'I weighed 96 pounds when I was the silver medalist,' " Dickerson says, " 'and that's the weight I'm going to stay.' "

It is common among models and dancers, overachievers, highly motivated types who are constantly monitoring their own success. "Yuppies get into eating disorders," Rubel says. "Almost all the women who get them are upwardly mobile people with the feeling that no matter how much they actually achieve, they aren't quite good enough. They always have to go that extra mile."

"No one would say running would cause the disorder," says Dr. Mona Shangold, assistant professor and director of the sports gynecology center at Georgetown University Hospital. "Someone obsessed with keeping her weight down may find running helpful."

Jack Daniels, research exercise physiologist at Athletics West, says, "My observation is that is it much worse among people who are pretty good and trying to get great than in great people trying to get greater. It's always the ones trying to reach something just beyond their ability."

Physiology reinforces the compulsion. Lowered body fat does improve performance. "But there is a reversal of that, a 180-degree shift past a certain point," Pengelly says. "They improve their performance by adding more miles and increasing the intensity of their workouts, by taking off pounds and reducing their body fat until they lose perspective. They look like they're competing for Athletes for Auschwitz. You're looking at very little muscle tone, faces that are gaunt. Their eyes, when you look closely, don't sparkle. They look like they've just come out of a concentration camp."

Consider Mary Wazeter. She is 21 now, a former runner.

"I became anorexic my senior year in high school," she says. "I ran in the cross country nationals in California, the high school ones. All of a sudden it seemed to me that so many of the girls were thinner than I was. It was a distortion of reality, but I decided to lose 10 pounds and improve my running. I went from 105 pounds to 95 that January."

She is 5 feet 4. She became obsessed with food, with counting calories. Her weight dropped to 89 pounds. She became anemic, weak, scared. She put on some weight and won a state track championship and a scholarship to Georgetown.

"That summer my mind was really affected with food obsessions. I couldn't concentrate. I couldn't read. I started going to road races. I started eating regimentally. If I weighed 96, I panicked. I had to be 95. I thought, 'This is my perfect running weight.' I'd see a picture of what I ate in the back of my mind. When I ran I would hear voices of what I ate."

She says she was "just hanging on by a thread."

"I didn't tell anyone. I went away to school. I became disoriented. I started getting lost around campus. I was losing things. I dropped to 85 pounds. I kept getting more and more panicky.

"I swung to the other end, like bulimia," she says. "I never threw up. I'd be so hungry. I'd eat cookies, candy, then go running. I became more and more depressed because I wasn't the runner I wanted to be. I didn't realize I had anorexia. I thought I was going crazy.

"Finally I entered Georgetown psychiatric unit. They kept wanting me to put on weight. Things got worse. I went from 85 pounds to 98 in three weeks. Now I felt fat and I wasn't able to run. My dream was to go to Georgetown and run, and my world had ended."

She was diagnosed as suicidal. She left Georgetown after two months and went home to Wilkes-Barre, Pa., where she was hospitalized again. The night after she was released, she tried to kill herself. "That's when I ended up taking my life, trying to take my life," she says. "I jumped off a railroad bridge."

She is now paralyzed from the chest down. She is a sophomore at Kings College, majoring in geology. She goes to school part time because the damage to her spinal cord makes it difficult to sit up for long periods. "I go to school on a cot," she says.

She also swims every day. But she does not count the laps. "I've been delivered from compulsiveness," she says. "I don't swim like I used to run."

Marianne Dickerson eats breakfast now. She has a new diet -- lots of vegetables and whole grains and very little red meat, which chagrins her father the meat salesman. The color has returned to her face. She has put on 10 pounds. She used to weigh herself every day. She hasn't been on a scale in the last month.

"I feel like I'm walking around with a backpack on my back," she says, laughing. "I look healthy. My face filled out. Maybe I'm not running as well, but it's nice. I get comments -- 'Gosh, you look good.' "

She is 24 now. She luxuriates in the sensation of energy. She is finishing her graduate degree in engineering at the University of Michigan. She is looking for a job and is racing again. She believes she will run as well as she once did. Running was not the problem, she says, abusing it was.

"I think about it all the time. I told my mom, 'If I had a choice to weigh what I weighed and feel the way I felt and look the way I looked and not quite be running at that level, I'd much rather be the way I am.' If I had to sacrifice my body to be at that level, I wouldn't do it.

"It's not a funny subject," she says. "And I want people to know how good you feel if you put on 10 or 15 pounds and reach a normal weight. But the only bad thing that has happened to me is that I have nothing left to wear."