The teen-age girl wearing the white blouse and the gold chain with somebody else's class ring on it stood around the stage yesterday watching the people dressed as carrots, peas and a salt shaker. They sang: "If you listen to my point of view, you will know vegetables are good for you" to the tune of "Fifty Ways to Leave Your Lover."

"I ain't never seen anything like this in my life," the teen-ager said, shaking her head as the vegetables danced off the stage of the Breakfast, Lunch and Dinner Theater, one of 60 exhibits promoting disease preventation at the Health Works '79 fair.

The fair, the first of its kind and sponsored by the U.S. Department of Health, Education and Welfare, at Independence Avenue and Third Street NW, is open today and tomorrow from 10 a.m. to 5 p.m.

"Everybody knows some nutrition information, but what we are trying to do is to jab them, to get them to have fun and learn more at the same time," said Nancy Low, director of the fair. "My feeling is that, until now, nutrition information was handled in a very uninteresting way."

Low and other HEW officials, calling HealthWorks '79 a prototype of fairs they would like to see sponsored nationwide, said they hoped a somewhat unorthodox presentation of factual information would spark interest in disease prevention.

Not all the exhibits at HealthWorks were as creative as the "nutrition musical" at the theater, sponsored by the National Institutes of Health. But some were unusual for health fairs, including Nutro the Robot, who scared fifth-grader Tracy Thompson of Payne Elementary School in the city, when he (the robot) spoke about the advantages of eating properly.

"The robot scared me when he first turned on," said Thompson, who was invited to dance on the stage with Nutro, who held out padded mechanical paws and said, "Give me five."

"What did I learn from the fair?" said Thompson, 12, her hair tied in corn rows and wearing a peach-coloured dress. "I learned what to eat, what's good for your teeth and to brush after every meal.

"I do brush after every meal now, except when I'm in school and of course I can't brush now 'cause I'm here on a trip," she said.

There were demonstrations of how to prepare nutritious snacks from fresh fruits and vegetables, physical fitness testing and blood pressure checks, t'ai-chi and yoga as ways to relieve tension, information on how to prevent tooth decay, and auto safety features shown by the Department of Transportation.

HEW secretary Joseph A. Califano said the fair, which cost $170,000, was "less than one CAT scanner (a type of X-ray machine) and we already have more than we need in this country. As communities learn to do more of this kind of thing, I'm sure that it can be done more cheaply."

Inside the "stress tent," where volunteers demonstrated the effects of stress and how to avoid it, Sarah Adkinson, a Southeast Washington resident, stretched out on a yellow bean bag with three electrode modules taped to her forehead.

Thompson, who came to the fair with a busload of senior citizens from the Johnson Senior Citizen Center in the city, closed her eyes and tried to relax as Dr. Dale Berman explained to others around her how tension affects the muscles of the body.

"Grind your teeth, Sarah," said Berman, monitoring the temperature reader, electromyograph (a machine that records muscle activity) and the digital integrator machines that recorded Thompson's tension by loud beeps. As Thompson ground her teeth, the beeps grew louder, apparently showing her tension.

Later, Thompson said, "You know, that machine really shows the value of relaxing and letting go. It's something to think about. It's the first test I have ever had like that."